It probably depends on where in Germany you are. One time in Berlin I started on my broken German and they reacted with a big question mark, and then back to English.
And 20-30 years ago you had to use German most places.
when my dad was stationed in germany all he ever learned to say was “which way to the train station?”
So he literally “only understands train station”.
“Verstehe nur Bahnhof” is a common German expression to say that you have no idea what someone just said (because of jargon, or whatever), which supposedly comes from people that came to Germany and only new/understood “train station”.