You'll have to learn that by yourself, dude.

Apart from confusion in the use of 'for' and 'to' as prepositions, many French and Italian students have problems with 'for' infront of the infinitive of the verb to denote purpose. In English we say 'I went to the supermarket 'to buy' some milk'. The infinitive here denotes the purpose of the visit to the supermarket so 'for' is not necessary. In French and Italian they say 'I went to the supermarket for to buy some milk' as the infinitive does not denote purpose. Since you speak French Maksen, I thought you might be having a problem with this too. :)

Use "to" to express 1. destination : We’re going to Paris. 2. before (in time) : It’s a quarter to 2. 3. until : We’ll be in the office from 5 to 6. 4. comparison :He won by 2 games to 3. I prefer sleeping to working. 5. receiver: I gave the present to her. Use "for" to express 1. “intended to belong to” : This is for you. 2. length of time : We’ve lived here for 2 years. 3. an arrangement : I made an appointment for May 3. 4. “in favor of” : Are you for or whaling? 5. reason : What did you do that for? 6. purpose ( + noun) : Let’s go out for a meal. 7. movement towards : They left for America this morning. 8. on behalf of (to help somebody) : I’ve cut my finger. Could you please write a note for me?