Earlier quoted context omitted.
We took that train, realised when we got to the other end of the line that we hadn't gotten where we expected, then turned back to the place where it separates. Waited for the next advertised train to airport (it's signalled on the electronic board as two separate entries; yes, it says "board whatever carriages for airport, and the rest for ...", or at least I assume it did, as it was in German of course; but again,…
American Express I get. No one uses that in Europe. Visa and Mastercard debit cards are what everyone uses and they work in all German ticket machines. You weren't trying to use a credit card where you? What language do you expect the Germans to use?
Managed 2 weeks in the UK without touching cash and the transactions between currency were inexpensive and quick.
Massive fan.