diff --git a/backend/services/vocabService.js b/backend/services/vocabService.js
index 717d168..52c8ceb 100644
--- a/backend/services/vocabService.js
+++ b/backend/services/vocabService.js
@@ -612,15 +612,10 @@ export default class VocabService {
     // Kombiniere alle AND-Bedingungen
     // Wenn sowohl andConditions als auch direkte where-Eigenschaften existieren,
     // müssen sie kombiniert werden
-    const directWhereProps = Object.keys(where).filter(key => key !== Op.and && key !== Op.or);
-    
-    // Debug: Prüfe, ob direkte Eigenschaften gesetzt wurden
-    console.log(`[getCourses] Debug - Vor Kombination:`, {
-      directWhereProps,
-      whereKeys: Object.keys(where),
-      andConditionsLength: andConditions.length,
-      languageId,
-      nativeLanguageId
+    // WICHTIG: directWhereProps muss NACH dem Setzen aller direkten Eigenschaften berechnet werden
+    const directWhereProps = Object.keys(where).filter(key => {
+      // Filtere Op.and und Op.or heraus (sind Symbol-Keys)
+      return key !== Op.and && key !== Op.or && typeof key === 'string';
     });
     
     if (andConditions.length > 0) {
@@ -632,15 +627,18 @@ export default class VocabService {
           delete where[key];
         }
         andConditions.push(directWhere);
-        console.log(`[getCourses] Debug - Direkte Eigenschaften zu andConditions hinzugefügt:`, directWhere);
       }
-      where[Op.and] = andConditions;
-      console.log(`[getCourses] Debug - Finale andConditions:`, JSON.stringify(andConditions, null, 2));
+      // Entferne leere Objekte aus andConditions
+      const filteredConditions = andConditions.filter(cond => {
+        return cond && typeof cond === 'object' && Object.keys(cond).length > 0;
+      });
+      // Setze andConditions nur, wenn sie nicht leer sind
+      if (filteredConditions.length > 0) {
+        where[Op.and] = filteredConditions;
+      }
     }
-    // Wenn nur direkte Eigenschaften existieren (undConditions.length === 0),
+    // Wenn nur direkte Eigenschaften existieren (andConditions.length === 0),
     // bleiben sie in where (nichts zu tun, sie sind bereits dort)
-    
-    console.log(`[getCourses] Debug - Finale WHERE-Klausel:`, JSON.stringify(where, null, 2));
 
     const courses = await VocabCourse.findAll({
       where,
@@ -666,17 +664,37 @@ export default class VocabService {
     // Lade Sprachnamen für alle Kurse
     const languageIds = [...new Set(coursesData.map(c => c.languageId))];
     if (languageIds.length > 0) {
-      const [languages] = await sequelize.query(
+      const languages = await sequelize.query(
         `SELECT id, name FROM community.vocab_language WHERE id IN (:languageIds)`,
         {
           replacements: { languageIds },
           type: sequelize.QueryTypes.SELECT
         }
       );
-      const languageMap = new Map(languages.map(l => [l.id, l.name]));
-      coursesData.forEach(c => {
-        c.languageName = languageMap.get(c.languageId) || null;
-      });
+      if (Array.isArray(languages)) {
+        const languageMap = new Map(languages.map(l => [l.id, l.name]));
+        coursesData.forEach(c => {
+          c.languageName = languageMap.get(c.languageId) || null;
+        });
+      }
+    }
+    
+    // Lade Muttersprachen-Namen für alle Kurse
+    const nativeLanguageIds = [...new Set(coursesData.map(c => c.nativeLanguageId).filter(id => id !== null))];
+    if (nativeLanguageIds.length > 0) {
+      const nativeLanguages = await sequelize.query(
+        `SELECT id, name FROM community.vocab_language WHERE id IN (:nativeLanguageIds)`,
+        {
+          replacements: { nativeLanguageIds },
+          type: sequelize.QueryTypes.SELECT
+        }
+      );
+      if (Array.isArray(nativeLanguages)) {
+        const nativeLanguageMap = new Map(nativeLanguages.map(l => [l.id, l.name]));
+        coursesData.forEach(c => {
+          c.nativeLanguageName = c.nativeLanguageId ? nativeLanguageMap.get(c.nativeLanguageId) || null : null;
+        });
+      }
     }
 
     return coursesData;