diff --git a/app/app.py b/app/app.py
index d20cfe2..9a2620d 100644
--- a/app/app.py
+++ b/app/app.py
@@ -11,8 +11,8 @@ app.config['SESSION_TYPE'] = 'filesystem'
 app.config['SESSION_FILE_DIR'] = './.flask_session/'
 Session(app)
 
-STRIPE_STARTING_COLS = ['Type', 'ID', 'Created', 'Description', 'Amount', 'Currency', 'Converted Amount', 'Fees', 'Net', 'Converted Currency', 'Details']
-RAISENOW_STARTING_COLS = ['Identifikationsnummer', 'Erstellt', 'UTC-Offset', 'Status', 'Betrag', 'Währung', 'Übernommene Gebühren - Betrag', 'Übernommene Gebühren - Währung', 'Zahlungsmethode', 'Zahlungsanbieter', 'Nettobetrag', 'Auszahlungswährung']
+STRIPE_STARTING_COLS = ['Type', 'ID', 'Created', 'Description', 'Amount', 'Currency', 'Converted Amount']
+RAISENOW_STARTING_COLS = ['Identifikationsnummer', 'Erstellt', 'UTC-Offset', 'Status', 'Betrag', 'Währung']
 
 
 def get_dataframe(key):
@@ -36,7 +36,7 @@ def get_merged_df(table_name): # return table_name: str
       - no pandas merge suffixes at all
       - all original columns (including Raisenow's norm_zweck) preserved
     """
-    print('calculated DataFrame')
+    print('calculate DataFrame...')
     # --- load & normalize Stripe ---
     stripe_import = get_dataframe('stripe_import')
     
@@ -125,10 +125,11 @@ def get_merged_df(table_name): # return table_name: str
     )
     # additional assignment: build a mask of rows where norm_zweck is still empty/NaN
     mask = raisenow['norm_zweck'].isna() | (raisenow['norm_zweck'] == '')
-    raisenow.loc[mask, 'norm_zweck'] = (
-        raisenow.loc[mask, 'raisenow_parameters.product.source_url']
-            .str.extract(r'https?://[^/]+/([^/?#]+)')[0]
-    )
+    if mask.any() and 'raisenow_parameters.product.source_url' in raisenow.columns:
+        raisenow.loc[mask, 'norm_zweck'] = (
+            raisenow.loc[mask, 'raisenow_parameters.product.source_url']
+                .str.extract(r'https?://[^/]+/([^/?#]+)')[0]
+        )
 
     # --- return raw tables if requested ---
     if table_name == 'stripe_import':
@@ -343,10 +344,10 @@ def upload():
         raw = (
             pd.read_csv(f) if f.filename.lower().endswith('.csv') else pd.read_excel(f)
         )
-        raw = raw.dropna(how='all').dropna(axis=1, how='all')
-        print('number of rows:', len(raw))
+        raw = raw.dropna(how='all')
         raw = raw.astype(object).replace({np.nan: None})
         cols = list(raw.columns)
+
         if cols[:len(STRIPE_STARTING_COLS)] == STRIPE_STARTING_COLS:
             key = 'stripe_import'
             dedupe_col = 'ID'
@@ -354,8 +355,12 @@ def upload():
             key = 'raisenow_import'
             dedupe_col = 'Identifikationsnummer'
         else:
-            continue
-
+            print('file does not match expected formats:', f.filename)
+            return jsonify({
+                "status": "error",
+                "message": f"File '{f.filename}' does not match expected formats."
+            }), 400
+        
         existing = get_dataframe(key)
         combined = pd.concat([existing, raw], ignore_index=True)
         deduped = combined.drop_duplicates(subset=[dedupe_col], keep='first').reset_index(drop=True)