Hai Alexandre... Basicly, "to & for are preposition. Preposition is a word that shows the relationship between a noun or pronoun and other words in a sentence. To Used to indicate the place, person, or thing that someone or something moves toward, or the direction of something: I am heading to the entrance of the building. Used to indicate a limit or an ending point: The snow was piled up to the roof. Used to indicate relationship : This letter is very important to your admission. Used to indicate a time or a period: I work nine to six, Monday to Friday. For Used to indicate the use of something: This place is for exhibitions and shows. Used to mean because of: I am so happy for you. Used to indicate time or duration: He’s been famous for many decades. For more examples click link http://www.talkenglish.com/Grammar/prepositions-of-to-for.aspx

This is a difficult question. "To" is generally used to show who or what is going to receive something or be moved toward; think of the word "toward." "For" is used similarly, but is more for the intent of movement. Here are some examples of the use of each: "I made a birdhouse for my uncle. I gave it to him." In this sentence, "for" is used to show who benefits for the action and "to" is used to show direction on the verb "gave." "I wrote a letter to my manager, it was for my resignation." In this sentence "for" is used to show why something is happening and "to" is used to show who the letter is intended for. "I made a cake for you, let me give it to you." In this example "for" shows the intent and "to" supports the action of the cake being given.

I'm not completely sure of this because I don't really speak Portuguese, but I thought (generally) "para" is "to", and "por" is "for".

I referred someone else here to this video the other day: https://www.youtube.com/watch?v=E3gvjrh5_TY Its topic is the use of "for" and "to" of course. It's good. :)