I'm a foreigner living in Germany for many years now. Before I got here I was fluent in four languages plus some basic German. Now I speak nearly fluent German, but back then it was really very basic. When I had to deal with Germans and they'd see my broken German, many would treat me like a complete idiot, assuming that not knowing German meant I didn't know anything about anything.

For example, the heater was broken in my apartment right after I moved in and I called some specialist to come in and have a look. I switched the heater off to avoid more damage since it wasn't working anyway. When the guy got there, first thing he did was to teach me, very slowly and in a very condescending way, to switch it on -- basic flip a switch. Then he asked me if I knew it was off, and if I hadn't confused it being off with being broken. Yeah, dude, I can see my breath inside my house and it never occurred to me to switch it off and on again... The nerve on some people.