Jonathan, I'm glad you're taking an interest in the Norwegian language, but I think your question is a little too broad. You shouldn't expect someone to come along and give you an entire lecture on the use of prepositions in Norwegian. There are tons of articles that should be able to give you an introduction. Try googling something like "prepositions in Norwegian" or "Norwegian prepositions" and you'll get tons of results. Look through the top three results and I'm sure you'll get a nice overview. If, after having read through those web pages, you're still unclear on something, then please, by all means, come back here and we'll help you clear it up. The thing is, if you ask a more specific question, you're gonna get more responses from the community. Good luck! :-)

Thanks for always help Christine :)

PS: If you have a textbook to guide you in your language learning - or you are perhaps following a structured course online, the usage of the main prepositions will usually be covered quite early on in the course, with some helpful explanations. Having access to those kinds of tools would of course make it easier for you to apply what I have suggested above :)

So, for example, if you want to be able to tell someone where you are going on a trip next summer, you might learn a sentence like this: "Jeg skal reise TIL (...) neste sommer". If you want to tell someone that you are going to play the guitar at a friend's party, you might learn a sentence like this one: "Jeg skal spille gitar PÅ festen." Or perhaps you'd prefer to use this one: "Jeg skal spille gitar FOR gjestene." If, let's say, you are going shopping for your grandmother tomorrow, you might learn a sentence like this one: "Jeg skal handle FOR bestemor i morgen." These examples all happen to correspond quite nicely with their English equivalents - however, this is often not the case. So, when in doubt - simply post another question here, letting us know what it is you want to express, and I'm sure you will get some useful help from the italki community. It's great to know that you are learning Norwegian - I wish you the best of luck :)

I see that you have specified your question a little bit further in your comment to André's answer. Don't get discouraged - you are not alone finding prepositions challenging :) One of the interesting things about prepositions, is that they quite often cannot be translated directly between languages (as I understand you have already experienced). Also, they are often part of fixed expressions, or idioms, that you'll just have to pick up gradually as you make more progress in the language. I would definitely NOT suggest you now go ahead and memorise every possible way in which "to" and "for" are used differently in Norwegian, compared to the way their equivalent prepositions are used in Portuguese and English. The best way to learn prepositions (in my opinion), is within a context that is relevant to your situation - focusing on what it is you want to be able to express in your everyday life. By this, I mean that it would be a good idea to learn the Norwegian way of using the various prepositions little by little, mainly within specific sentences that you want to be able to say.