Drop off close on Sunday after 9pm in Munich Central Train Station not define

We got a new Audi A4 - an upgrade from what we ordered (Skoda Kodiaq). It took some convincing however, as we were offered a smaller car at first.

We picked up the car at Munich Airport. After we declined the offer for a larger car and additional insurance, the staff gave us the keys and told us to find the car ourselves. The instructions were unclear, and we spent a very long time looking for it.

Picked up the car in the morning when there were few people. The first car they gave us was a JEEP, and they said there were no other models available. The front window had a crack longer than 10cm, so they replaced it with another car which still had a small crack on the front window, but they assured us it was fine to drive.

The attitude was acceptable, but they forced me to upgrade the car model and charged extra. Showing the QEEQ order was useless. After I signed, the staff left the counter and ignored me. There was no queue that day; it was a free moment.

After returning the car in Munich and boarding the train to Frankfurt, I realized that I hadn't returned the keys. I proactively called to ask if I should send them back via DHL from Frankfurt or return them to Europcar at Frankfurt Airport. After a while, the branch called back, insisting that I must come back immediately and take full responsibility for any consequences. I explained that I had an international flight connection and couldn't just jump off the train. They kept insisting that I return immediately or face huge fines.