It's true you can't translate words between languages exactly. Nor can you translate any individual's meaning of a word exactly into another individual's meaning of the word within a language! When I think of "nostalgia" I get a very particular sequence of mental images and emotions, tied in with my particular life experiences, doubtless different from yours.

But it is not hard to translate between languages within the same epsilon of error that holds for translation between speakers within a language.