“Why?” is the question (Por que?). “Because” introduces the answer (Porque). Example: — Why are you here? — Because I want to practice English. Exemplo: — Por que você está lá? — Porque eu quero praticar o inglês.

"Because" and "Why" are very different words. Have you looked them up in the dictionary? Have you compared them to similar words in your language? If you look these words up in the dictionary, you should be able to find the answer very easily. Try to write some sample sentences with these words so we can see what it is you don't understand about them.