diff --git a/webseite/topicEditor.php b/webseite/topicEditor.php
index 8886dab..51a69ac 100644
--- a/webseite/topicEditor.php
+++ b/webseite/topicEditor.php
@@ -52,8 +52,8 @@ if (isset($_GET['subject']) && isset($_GET['topic'])) {
         $defaultValues['formulas'] = implode(";;;;", $tasks);
         $defaultValues['article'] = $editingTopic->getFinishedArticle();
     }
-} else if (isset($_GET['subject'])) {
-    $defaultValues['subjectId'] = $_GET['subject'];
+} else if (isset($_GET['subjectId'])) {
+    $defaultValues['subjectId'] = $_GET['subjectId'];
 }
 
 if ($_SERVER['REQUEST_METHOD'] == 'POST') {
@@ -350,10 +350,33 @@ if ($_SERVER['REQUEST_METHOD'] == 'POST') {
                            id="relatedTopicSelect"
                            class="w-full px-4 py-3 border rounded-lg focus:outline-none focus:ring-2 focus:ring-blue-500 text-lg enabled:hover:border-gray-400"
                            value="<?php echo $defaultValues['relatedTopics']; ?>">
+
+
+                    <?php
+                    if ($defaultValues['subjectId'] !== "") {
+                        ?>
+                        <select id="addRelatedTopic"
+                                onchange="addSelectedRelatedTopic()"
+                                class="w-full px-4 py-3 border rounded-lg focus:outline-none focus:ring-2 focus:ring-blue-500 text-lg enabled:hover:border-gray-400 appearance-none bg-white">
+                            <option selected value="">Thema hinzufügen</option>
+                            <?php
+
+                            foreach ($allSubjects[$defaultValues['subjectId']]->getTopics() as $topic) {
+                                if(isset($editingTopic) && $topic->getId() === $editingTopic->getId()) {
+                                    continue;
+                                }
+
+                                echo "<option value='" . $topic->getId() . "'>" . $topic->getDisplayName() . "</option>";
+                            }
+                            ?>
+                        </select>
+                        <?php
+                    }
+                    ?>
                 </div>
 
                 <div>
-                    <label for="existing_files" class="block text-sm font-medium text-gray-700 mb-2">Existierende Übungsblätter</label>
+                    <label for="existing_files" class="block text-sm font-medium text-gray-700 mb-2">Existierende Übungsblätter - Entfernen zum Löschen</label>
                     <input type="text"
                            name="existing_files"
                            id="existing_files"
@@ -425,6 +448,12 @@ if ($_SERVER['REQUEST_METHOD'] == 'POST') {
             </div>
         </div>
 
+        <?php
+        foreach($errors as $error) {
+            echo $error;
+        }
+        ?>
+
         <div class="flow-root gap-4">
             <?php if (isset($editingTopic)) { ?>
                 <input type="submit" value="Thema löschen" name="submit"
@@ -525,6 +554,26 @@ if ($_SERVER['REQUEST_METHOD'] == 'POST') {
         iconInput.value = element.getAttribute('data-icon');
     }
 
+    function addSelectedRelatedTopic() {
+        const input = document.querySelector('#relatedTopicSelect');
+        const selector = document.querySelector('#addRelatedTopic');
+
+        if(selector.value === "") {
+            return;
+        }
+
+        if(input.value.includes(selector.value)) {
+            return;
+        }
+
+        if(input.value.trim() === "") {
+            input.value += selector.value;
+        } else {
+            input.value += ", " + selector.value;
+        }
+        selector.selectedIndex = 0;
+    }
+
 </script>
 
 </body>