I don't speak anything very well. The longer that you travel, you find out that you really don't even need to speak the language to get around and get things done, to live in those places. If you're somewhat resourceful and perceptive, you're pretty much going to know what's going on because human nature is human nature: they understand it, you understand it, and it works.
Certainly we do not need quantum mechanics for macroscopic objects, which are well described by classical physics - this is the reason why quantum mechanics seems so foreign to our everyday existence.