Actually, I'd like to know how I should say, for example, "Irei para
São Paulo no final de semana", "Meus pais costumam me visitar nos
finais de semana", "Terei que trabalhar neste final de semana", etc.
I will go to Sampa on the weekend.
I will go to Sampa on this weekend.
My parents often visit me on weekends (on the weekend).
My parents are in the habit of visting me on weekends (on the weekend).
I will have to work this weekend.
I will have to work on the weekend.
And I have another question about prepositions... I've read on internet these sentences (www.englishpage.com):
- Fred loves to go camping in the desert, but Kyle prefers to camp in the mountains. = Fred loves to camp in the desert, but Kyle prefers to go camping in the mountains.
(in the desert, in the mountains, in the woods, in the park, in the city, in the country, in the forest, but on the beach, on the mountain and at the seashore and at the river/lake/stream/ocean)
- While they were hiking on Ridgeback Mountain, Laurelle and Frank saw a bear in the woods. but "While they were hiking in the Tehachapi Mountains, Laurelle and Frank saw a bear in the woods."
Why in first sentence is written "IN the mountain", and in the second "ON Ridgeback Mountain"? (You have made a small but important error here. The text does not say "in the mountain" but "in the mountains". Read what I wrote below.)
"In the mountain" (note it is singular) would mean "inside the mountain, with the mountain on all sides of us". "On the mountain" (note that it is singular) is the correct choice. On the the hand, if "mountain" is in the plural", then "in" makes sense to our ears. It means there are mountains, hills, valleys, etc. around you, on all sides.
In Portuguese, "em" would sound fine with the plural or the singular, but in English this small mistake hurts our ears and eyes. It is just one more small thing to learn, accept, and use. As for "why", forget logic. Languages are seldom logical. Certain things have been said in a certain way for centuries, and learners can either accept them or constantly call attention to themselves by not speaking and writing as the natives do.
More questions? Fire away! (Ask more questions!)