I was teaching a class in Kazakhstan. I speak fluent Russian. We had interpreters to teach what we said to the class. One interpreter did not care for me and was telling the others what he thought. He was wining about a powerpoint I had that was in English he wanted the powerpoint in Russian. So that night I put the powerpoint in Russian. He asked the next day how the powerpoint was done. I told him" I did it because we are not all stupid" He looked at me and quit within the hour. He realized I understood everything he said. I was getting ready to fire him, and get another interpreter. He saved me the trouble.