diff --git a/.ai/mcp/mcp.json b/.ai/mcp/mcp.json
new file mode 100644
index 0000000..e69de29
diff --git a/.idea/php.xml b/.idea/php.xml
index 8e445c2..8d4f284 100644
--- a/.idea/php.xml
+++ b/.idea/php.xml
@@ -10,9 +10,7 @@
     <option name="highlightLevel" value="WARNING" />
     <option name="transferred" value="true" />
   </component>
-  <component name="PhpProjectSharedConfiguration" php_language_level="7.0">
-    <option name="suggestChangeDefaultLanguageLevel" value="false" />
-  </component>
+  <component name="PhpProjectSharedConfiguration" php_language_level="8.5" />
   <component name="PhpStanOptionsConfiguration">
     <option name="transferred" value="true" />
   </component>
diff --git a/content/deleteAccount.php b/content/deleteAccount.php
new file mode 100644
index 0000000..0bb31e1
--- /dev/null
+++ b/content/deleteAccount.php
@@ -0,0 +1,19 @@
+<?php
+require_once "php/model/LocalUserDAO.php";
+
+$dao = new LocalUserDAO();
+
+/*
+    Deregistrierung
+    Funktion: Entfernt User aus Dummy-Daten und beendet Session
+*/
+
+if (isset($_SESSION["user_email"])) {
+    $dao->deleteUser($_SESSION["user_email"]);
+}
+
+$_SESSION = [];
+session_destroy();
+
+header("Location: index.php");
+exit();
\ No newline at end of file
diff --git a/content/login.php b/content/login.php
index 9cdac36..8ca3bfe 100644
--- a/content/login.php
+++ b/content/login.php
@@ -1,32 +1,53 @@
+<?php
+$error = $error ?? null;
+?>
+
 <!--
     Form: Login-Bereich
     Funktion: Benutzerauthentifizierung und Zugang zum eigenen Profil, Erstellen von Beiträgen, etc.
 -->
 <main class="login-page">
     <div class="login-container">
-        
+
         <h1>Bitte anmelden</h1>
 
-        <form>
-            <label id ="inputEmail" class="screenreader-only">E-Mail Adresse / </label>
+        <?php if ($error): ?>
+            <p style="color:red;">
+                <?php echo htmlspecialchars($error); ?>
+            </p>
+        <?php endif; ?>
+
+        <form method="post" action="index.php?pfad=login">
 
             <p class="input-label">Benutzername/E-Mail-Adresse:</p>
-            <input type="email" name="email" class="login-input" placeholder="E-Mail-Adresse" required autofocus>
+            <input type="email"
+                   name="email"
+                   class="login-input"
+                   placeholder="E-Mail-Adresse"
+                   required
+                   autofocus>
 
             <p class="input-label">Passwort:</p>
-            <input type="password" name="password" class="login-input" placeholder="Passwort" required>
+            <input type="password"
+                   name="password"
+                   class="login-input"
+                   placeholder="Passwort"
+                   required>
 
-            <div class="checkbox-wrapper">
-                <label>
-                    <input type="checkbox" name="remember-me" value="1"> angemeldet bleiben
-                </label>
-            </div>
-
-            <button type="submit" value="anmelden" name="loginSubmit" class="login-button">anmelden</button>
+            <button type="submit"
+                    value="anmelden"
+                    name="loginSubmit"
+                    class="login-button">
+                anmelden
+            </button>
 
             <div class="register-link">
-                <a href="register.php">Noch keinen Account? Jetzt hier registrieren!</a>
+                <a href="index.php?pfad=register">
+                    Noch keinen Account? Jetzt hier registrieren!
+                </a>
             </div>
+
         </form>
+
     </div>
 </main>
\ No newline at end of file
diff --git a/content/logout.php b/content/logout.php
new file mode 100644
index 0000000..49386ab
--- /dev/null
+++ b/content/logout.php
@@ -0,0 +1,6 @@
+<?php
+$_SESSION = [];
+session_destroy();
+
+header("Location: index.php");
+exit();
\ No newline at end of file
diff --git a/content/profile.php b/content/profile.php
index 769b4fb..1d9b970 100644
--- a/content/profile.php
+++ b/content/profile.php
@@ -1,46 +1,45 @@
-<!--
-    Content: Profil
-    Inhalt: Das eigene Profil, wenn man angemeldet ist. Dort hat man die Möglichkeit seine Angaben zu ändern.
--->
+<?php
+include_once 'php/controller/profile-controller.php';
+
+$user = $user ?? null;
+?>
 
 <main class="form-page">
-
     <div class="form-container">
+
+        <h1>Mein Profil</h1>
+
         <form>
-
-            <label class="input-label">Vorname</label>
-
-            <input type="text" name="Vorname" class="login-input" required
-                   placeholder="Vorname"
-                   value="<?php //DB-Daten ?>">
-
-            <label class="input-label">Nachname</label>
-            <input type="text" name="Nachname" class="login-input" required
-                   placeholder="Nachname"
-                   value="<?php //DB-Daten ?>">
+            <label class="input-label">Name</label>
+            <input type="text"
+                   class="login-input"
+                   readonly
+                   value="<?php echo htmlspecialchars($user["username"] ?? ""); ?>">
 
             <label class="input-label">Email-Adresse</label>
-            <input type="email" name="Email" class="login-input" required
-                   placeholder="mustermann@web.de"
-                   value="<?php //DB-Daten ?>">
+            <input type="email"
+                   class="login-input"
+                   readonly
+                   value="<?php echo htmlspecialchars($user["email"] ?? ""); ?>">
 
             <label class="input-label">Passwort</label>
-            <input type="password" name="Passwort" class="login-input"
-                   required placeholder="Passwort">
-
-            <br>
-
-            <button type="submit" class="login-button">
-                Speichern
-            </button>
-
-            <br><br>
-
-            <button type="button" class="login-button">
-                Account löschen
-            </button>
-
+            <input type="password"
+                   class="login-input"
+                   readonly
+                   value="********">
         </form>
 
+        <br>
+
+        <a href="index.php?pfad=deleteAccount" class="login-button">
+            Account löschen
+        </a>
+
+        <br><br>
+
+        <a href="index.php?pfad=logout" class="login-button">
+            Abmelden
+        </a>
+
     </div>
 </main>
\ No newline at end of file
diff --git a/content/register.php b/content/register.php
index c64ca53..0c19ebe 100644
--- a/content/register.php
+++ b/content/register.php
@@ -1,3 +1,9 @@
+<?php
+include_once 'php/controller/register-controller.php';
+
+$error = $error ?? null;
+?>
+
 <!--
     Form: Registrierung
     Funktion: Erstellung neuer Benutzerkonten
@@ -7,26 +13,50 @@
 
         <h1>Jetzt Registrieren!</h1>
 
-        <form>
+        <?php if ($error): ?>
+            <p style="color:red;">
+                <?php echo htmlspecialchars($error); ?>
+            </p>
+        <?php endif; ?>
+
+        <form method="post" action="index.php?pfad=register">
+
             <p class="input-label">Email:</p>
-            <input type="email" name="email" class="login-input" placeholder="mustermann@web.de" required>
+            <input type="email"
+                   name="email"
+                   class="login-input"
+                   placeholder="mustermann@web.de"
+                   required>
 
             <p class="input-label">Vorname:</p>
-            <input type="text" name="vorname" class="login-input" placeholder="Max" required>
+            <input type="text"
+                   name="vorname"
+                   class="login-input"
+                   placeholder="Max"
+                   required>
 
             <p class="input-label">Nachname:</p>
-            <input type="text" name="nachname" class="login-input" placeholder="Mustermann" required>
+            <input type="text"
+                   name="nachname"
+                   class="login-input"
+                   placeholder="Mustermann"
+                   required>
 
             <p class="input-label">Passwort:</p>
-            <input type="password" name="password" class="login-input" placeholder="Passwort" required>
+            <input type="password"
+                   name="password"
+                   class="login-input"
+                   placeholder="Passwort"
+                   required>
 
-            <div class="checkbox-wrapper">
-                <label>
-                    <input type="checkbox" value="remember-me"> angemeldet bleiben
-                </label>
-            </div>
+            <button type="submit"
+                    value="register"
+                    name="registerSubmit"
+                    class="login-button">
+                kostenlos registrieren
+            </button>
 
-            <button type="submit" value="anmelden" name="loginSubmit" class="login-button">kostenlos registrieren</button>
         </form>
+
     </div>
 </main>
\ No newline at end of file
diff --git a/data/users.json b/data/users.json
new file mode 100644
index 0000000..0637a08
--- /dev/null
+++ b/data/users.json
@@ -0,0 +1 @@
+[]
\ No newline at end of file
diff --git a/includes/navbar.php b/includes/navbar.php
index e8dd8ca..f1aa5a4 100644
--- a/includes/navbar.php
+++ b/includes/navbar.php
@@ -1,27 +1,41 @@
+<?php
+session_start();
+?>
+
 <!--
 Globales Menü, wird via PHP später in alle Seiten eingebunden
 -->
 <nav class="nav">
     <div class="nav__left">
         <a href="index.php" class="nav__logo">
-	        <img src="images/logos/logo_full.png" alt="Logo">
-	    </a>
+            <img src="images/logos/logo_full.png" alt="Logo">
+        </a>
     </div>
 
     <!-- Mobile navbar mit Burger-Symbol -->
     <input type="checkbox" id="nav-toggle" class="nav__checkbox">
     <label for="nav-toggle" id="mobile-nav">
-        <span>☰</span> <!-- Burger Icon Symbol -->
+        <span>☰</span>
     </label>
 
     <ul id="mobile-nav" class="nav__mobile-menu">
         <li>
             <label for="nav-toggle" class="nav__close-btn">&times;</label>
         </li>
-        <li><a href="index.php?pfad=profile">Profil</a></li>
-        <li><a href="index.php?pfad=login">Anmelden</a></li>
-        <li><a href="index.php?pfad=register">Registrieren</a></li>
-        <li><a href="index.php?pfad=createArticle">Beitrag erstellen</a></li>
+
+        <?php if (isset($_SESSION['user'])): ?>
+
+            <li><a href="index.php?pfad=profile">Profil</a></li>
+            <li><a href="index.php?pfad=logout">Abmelden</a></li>
+            <li><a href="index.php?pfad=createArticle">Beitrag erstellen</a></li>
+
+        <?php else: ?>
+
+            <li><a href="index.php?pfad=login">Anmelden</a></li>
+            <li><a href="index.php?pfad=register">Registrieren</a></li>
+
+        <?php endif; ?>
+
         <li>
             <label class="nav__mobile-label">Sprachen</label>
             <ul class="nav__mobile-submenu">
@@ -39,7 +53,7 @@ Globales Menü, wird via PHP später in alle Seiten eingebunden
                 <li><a href="index.php?pfad=mathe">Mathematik</a></li>
                 <li><a href="index.php?pfad=biologie">Biologie</a></li>
                 <li><a href="index.php?pfad=chemie">Chemie</a></li>
-                <li><a href="index.php?pfad=englisch">Physik</a></li>
+                <li><a href="index.php?pfad=physik">Physik</a></li>
                 <li><a href="index.php?pfad=informatik">Informatik</a></li>
                 <li><a href="index.php?pfad=astronomie">Astronomie</a></li>
             </ul>
@@ -85,6 +99,7 @@ Globales Menü, wird via PHP später in alle Seiten eingebunden
                 <a href="index.php?pfad=literatur">Literatur</a>
             </div>
         </div>
+
         <div class="nav__item nav__dropdown">
             <button class="nav__dropdown-toggle">MINT</button>
             <div class="nav__dropdown-menu">
@@ -96,6 +111,7 @@ Globales Menü, wird via PHP später in alle Seiten eingebunden
                 <a href="index.php?pfad=astronomie">Astronomie</a>
             </div>
         </div>
+
         <div class="nav__item nav__dropdown">
             <button class="nav__dropdown-toggle">Gesellschaft & Werte</button>
             <div class="nav__dropdown-menu">
@@ -112,6 +128,7 @@ Globales Menü, wird via PHP später in alle Seiten eingebunden
                 <a href="index.php?pfad=theater">Theater</a>
             </div>
         </div>
+
         <div class="nav__item nav__dropdown">
             <button class="nav__dropdown-toggle">Technik & Praxis</button>
             <div class="nav__dropdown-menu">
@@ -124,14 +141,40 @@ Globales Menü, wird via PHP später in alle Seiten eingebunden
     </div>
 
     <div class="nav__right">
-        <a href="index.php?pfad=profile" class="nav_item nav__link">Profil</a>
-        <div class="nav__search">
-        <?php
-            include_once 'search.php';
-        ?>
-        </div>
-	    <a href="index.php?pfad=login" class="nav__item nav__button">Anmelden</a>
-	    <a href="index.php?pfad=register" class="nav__item nav__button">Registrieren</a>
-        <a href="index.php?pfad=createArticle" class="nav__item nav__button">Beitrag erstellen</a>
+
+        <?php if (isset($_SESSION['user'])): ?>
+
+            <a href="index.php?pfad=profile" class="nav__item nav__link">
+                Profil
+            </a>
+
+            <a href="index.php?pfad=createArticle" class="nav__item nav__button">
+                Beitrag erstellen
+            </a>
+
+            <div class="nav__search">
+                <?php include_once 'search.php'; ?>
+            </div>
+
+            <a href="index.php?pfad=logout" class="nav__item nav__button">
+                Abmelden
+            </a>
+
+        <?php else: ?>
+
+            <div class="nav__search">
+                <?php include_once 'search.php'; ?>
+            </div>
+
+            <a href="index.php?pfad=login" class="nav__item nav__button">
+                Anmelden
+            </a>
+
+            <a href="index.php?pfad=register" class="nav__item nav__button">
+                Registrieren
+            </a>
+
+        <?php endif; ?>
+
     </div>
 </nav>
\ No newline at end of file
diff --git a/index.php b/index.php
index a333e59..c6743e2 100644
--- a/index.php
+++ b/index.php
@@ -1,51 +1,71 @@
-
 <?php
 session_start();
-if (!isset($abs_path)) {
-    require_once "path.php";
+ob_start();
+
+$pfad = $_GET["pfad"] ?? "home";
+
+/*
+    Controller für Aktionen werden vor der HTML-Ausgabe geladen,
+    damit Weiterleitungen mit header() funktionieren.
+*/
+if ($pfad === "login") {
+    include_once "php/controller/login-controller.php";
+}
+
+if ($pfad === "register") {
+    include_once "php/controller/register-controller.php";
+}
+
+if ($pfad === "logout") {
+    include_once "content/logout.php";
+    exit();
+}
+
+if ($pfad === "deleteAccount") {
+    include_once "content/deleteAccount.php";
+    exit();
 }
-require_once $abs_path . "/php/controller/index-controller.php";
 ?>
 
-<!--
-    Seite: Index der Lernplattform
-    Funktion: Webseitengerüst, Anzeigen von Content
--->
-<!DOCTYPE html>
-<html lang="de">
+    <!--
+        Seite: Index der Lernplattform
+        Funktion: Webseitengerüst, Anzeigen von Content
+    -->
+    <!DOCTYPE html>
+    <html lang="de">
 
-<head>
-    <meta charset="utf-8">
-    <meta name="description" content="EduForge">
-    <meta name="author" content="Niklas Ortmann">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
-    <link rel="icon" type="image/x-icon" href="images/logos/logo_icon.ico">
-    <link rel="stylesheet" href="css/main.css">
-    <link rel="stylesheet" href="css/navbar.css">
-    <link rel="stylesheet" href="css/footer.css">
-    <link rel="stylesheet" href="css/search-results.css">
-    <link rel="stylesheet" href="css/createArticle.css">
-    <link rel="stylesheet" href="css/showArticle.css">
-    <link rel="stylesheet" href="css/message.css">
-    <title>EduForge</title>
-</head>
+    <head>
+        <meta charset="utf-8">
+        <meta name="description" content="EduForge">
+        <meta name="author" content="Niklas Ortmann">
+        <meta name="viewport" content="width=device-width, initial-scale=1.0">
+        <link rel="icon" type="image/x-icon" href="images/logos/logo_icon.ico">
+        <link rel="stylesheet" href="css/main.css">
+        <link rel="stylesheet" href="css/navbar.css">
+        <link rel="stylesheet" href="css/footer.css">
+        <title>EduForge</title>
+    </head>
 
+    <body>
 
-<body>
     <?php
     include_once 'includes/navbar.php';
-	//Dynamischer Inhalt:
-    if (isset($_GET["pfad"])) {
-        if (file_exists($abs_path . '/content/' . $_GET["pfad"] . '.php')) {
-            include_once $abs_path . '/content/' . $_GET["pfad"] . '.php';
-        } else {
-            include_once $abs_path . '/content/404.php';
-        }
-    } else {
-        include_once $abs_path . '/content/home.php';
-    }
-    include_once $abs_path . '/includes/footer.php';
-    ?>
-</body>
 
-</html>
\ No newline at end of file
+    /*
+        Dynamischer Inhalt:
+        Je nach pfad-Parameter wird die passende Datei aus content geladen.
+    */
+    if (file_exists('content/' . $pfad . '.php')) {
+        include_once 'content/' . $pfad . '.php';
+    } else {
+        include_once 'content/404.php';
+    }
+    include_once 'includes/footer.php';
+    ?>
+
+    </body>
+    </html>
+
+<?php
+ob_end_flush();
+?>
\ No newline at end of file
diff --git a/php/controller/login-controller.php b/php/controller/login-controller.php
new file mode 100644
index 0000000..642b39a
--- /dev/null
+++ b/php/controller/login-controller.php
@@ -0,0 +1,30 @@
+<?php
+
+require_once "php/model/LocalUserDAO.php";
+
+$dao = new LocalUserDAO();
+$error = null;
+
+/*
+    Verarbeitung des Login-Formulars
+    Funktion: Prüft Benutzerdaten und erstellt Session für eingeloggten Nutzer
+*/
+if ($_SERVER["REQUEST_METHOD"] === "POST") {
+
+    $email = $_POST["email"] ?? "";
+    $password = $_POST["password"] ?? "";
+
+    $user = $dao->findUser($email);
+
+    if ($user && password_verify($password, $user["password"])) {
+
+        $_SESSION["user"] = $user["username"];
+        $_SESSION["user_email"] = $user["email"];
+
+        header("Location: index.php");
+        exit();
+
+    } else {
+        $error = "Login fehlgeschlagen. Bitte überprüfe deine Eingaben.";
+    }
+}
diff --git a/php/controller/profile-controller.php b/php/controller/profile-controller.php
new file mode 100644
index 0000000..c731942
--- /dev/null
+++ b/php/controller/profile-controller.php
@@ -0,0 +1,20 @@
+<?php
+
+require_once "php/model/LocalUserDAO.php";
+
+$dao = new LocalUserDAO();
+
+if (!isset($_SESSION["user"])) {
+    header("Location: index.php?pfad=login");
+    exit();
+}
+
+$user = $dao->findUser($_SESSION["user_email"] ?? "");
+
+if (!$user) {
+    $_SESSION = [];
+    session_destroy();
+
+    header("Location: index.php?pfad=login");
+    exit();
+}
\ No newline at end of file
diff --git a/php/controller/register-controller.php b/php/controller/register-controller.php
new file mode 100644
index 0000000..d813d06
--- /dev/null
+++ b/php/controller/register-controller.php
@@ -0,0 +1,40 @@
+<?php
+
+require_once "php/model/LocalUserDAO.php";
+
+$dao = new LocalUserDAO();
+$error = null;
+
+/*
+    Verarbeitung des Registrierungs-Formulars
+    Funktion: Erstellt neuen Benutzer und speichert ihn im DAO + Session
+*/
+if ($_SERVER["REQUEST_METHOD"] === "POST") {
+
+    $email = $_POST["email"] ?? "";
+    $vorname = $_POST["vorname"] ?? "";
+    $nachname = $_POST["nachname"] ?? "";
+    $password = password_hash(
+        $_POST["password"] ?? "",
+        PASSWORD_DEFAULT
+    );
+
+    if ($dao->findUser($email)) {
+
+        $error = "Diese E-Mail-Adresse ist bereits registriert.";
+
+    } else {
+
+        $dao->addUser(
+            $email,
+            $vorname . " " . $nachname,
+            $password
+        );
+
+        $_SESSION["user"] = $vorname . " " . $nachname;
+        $_SESSION["user_email"] = $email;
+
+        header("Location: index.php");
+        exit();
+    }
+}
diff --git a/php/model/LocalUserDAO.php b/php/model/LocalUserDAO.php
new file mode 100644
index 0000000..63bd80c
--- /dev/null
+++ b/php/model/LocalUserDAO.php
@@ -0,0 +1,64 @@
+<?php
+require_once "UserDAOInterface.php";
+
+class LocalUserDAO implements UserDAOInterface {
+
+    private string $file = "data/users.json";
+
+    private function loadUsers() {
+        if (!file_exists($this->file)) {
+            return [];
+        }
+
+        $json = file_get_contents($this->file);
+        $users = json_decode($json, true);
+
+        return is_array($users) ? $users : [];
+    }
+
+    private function saveUsers($users) {
+        file_put_contents(
+            $this->file,
+            json_encode($users, JSON_PRETTY_PRINT)
+        );
+    }
+
+    public function findUser($email) {
+        $users = $this->loadUsers();
+
+        foreach ($users as $user) {
+            if ($user["email"] === $email) {
+                return $user;
+            }
+        }
+
+        return null;
+    }
+
+    public function addUser($email, $username, $password) {
+        $users = $this->loadUsers();
+
+        $users[] = [
+            "email" => $email,
+            "username" => $username,
+            "password" => $password
+        ];
+
+        $this->saveUsers($users);
+    }
+
+    public function deleteUser($email) {
+        $users = $this->loadUsers();
+
+        foreach ($users as $i => $user) {
+            if ($user["email"] === $email) {
+                unset($users[$i]);
+                $users = array_values($users);
+                $this->saveUsers($users);
+                return true;
+            }
+        }
+
+        return false;
+    }
+}
\ No newline at end of file
diff --git a/php/model/UserDAOInterface.php b/php/model/UserDAOInterface.php
new file mode 100644
index 0000000..721b887
--- /dev/null
+++ b/php/model/UserDAOInterface.php
@@ -0,0 +1,36 @@
+<?php
+
+/**
+ * Interface für den Zugriff auf Benutzerdaten.
+ *
+ * Definiert die Methoden, die jede UserDAO-Implementierung
+ * bereitstellen muss.
+ */
+interface UserDAOInterface {
+
+    /**
+     * Sucht einen Benutzer anhand seiner E-Mail-Adresse.
+     *
+     * @param string $email E-Mail-Adresse des gesuchten Benutzers
+     * @return array|null Benutzerdaten als Array oder null
+     */
+    public function findUser($email);
+
+    /**
+     * Fügt einen neuen Benutzer hinzu.
+     *
+     * @param string $email E-Mail-Adresse des Benutzers
+     * @param string $username Benutzername des Benutzers
+     * @param string $password Passwort des Benutzers
+     * @return void
+     */
+    public function addUser($email, $username, $password);
+
+    /**
+     * Löscht einen Benutzer anhand seiner E-Mail-Adresse.
+     *
+     * @param string $email E-Mail-Adresse des zu löschenden Benutzers
+     * @return bool true, wenn der Benutzer gelöscht wurde, sonst false
+     */
+    public function deleteUser($email);
+}
\ No newline at end of file