Does it really have all these meanings?
Translating prepositions (za, po, do, od, przed, u, w etc.) between languages is quite complicated and little useful, because every language has many exceptions (the fields of meanings are never identically correspondent).
Those words actually don't have much meaning if they stand alone, they acquire the flavour of their neighbours (i.e. of other words with stronger meaning, especially verbs, nouns and often out of the context).
Just remember the most important usage of them (start with the main usage of "po" = after, in regards to the time, so one thing happened after an other), in all other cases you'd rather have to learn to think in Polish, and you'll gradually comprehend more and more situations when a certain preposition is required.