Once when planning to board a train in Germany early in the
morning, I discovered to my horror that my ticket needed to be validated
before being used. Unfortunately, at that time of the morning, there
weren't any employees at the information desk or elsewhere. The only
person I could find who might be able to help me was the driver of the
train. He saw me motioning to him and stepped out. What I should have asked was, "Am I allowed to use this ticket?" "Darf ich dieses Ticket benutzen?"
but the only thing I could think to ask was, "Arbeitet dieses Ticket?":
literally, "Does this ticket labor?" (At that time, I didn't know the word "funktionieren," which might have worked better.) I knew my words weren't conducive
to my meaning, so I tried some simple English when I saw the man was
confused and probably also upset that I had disturbed him. He scared me off by gruffly saying, "Wir sind in Deutschland! Wir sprechen Deutsch!" (We're in Germany! We speak German!)
Luckily I liked Germany so much anyway that I moved there later.