1. I understand
2. Train station
3. Lit; I understand only Trainstation

Where does this expression come from? I always imagined an old dude on the phone talking to someone and he can't make out anything the other person is saying except for the word 'Bahnhof'. It's an older expression but it still has good comedic value. It's just a classic that everyone has heard before. It is rude and casual but that won't bother no one.