I never heard about a language with such complexity about preposition as English (no offense). Take a look: "I've been studying English FOR two years", "I'm looking FOR a house to buy", "I cannot go TO there tonight. I'm too tired" and "I'm going TO Ireland next week".
Sadly, there's a bunch of functions that both can assume, I suppose (and I'm not counting with the remains ones [like in, at and so on]).
I cannot cover all of them here. And you have to get used to it.
But, I recommend to you just Google them (sorry about that, but is the truth). When you'll type to search them, try the "English page" and the "English Grammar online".
I'm not a native speaker, and I'm learning them too. However, I hope those tips can help you.