The problem is that many Brazilians do not know their own language, which is terrible! I see some horrible corrections on italki that confirm my theory [There are a few people that make great corrections, though]. In my opinion, learning another language is essential nowadays, but we must have, at least, a great knowledge of our own. How are we supposed to help foreigners to learn our language if we're bad at it, if we bring bad habits to written Portuguese? That's why, knowing our own language is important before attempting another one. Furthermore, I absolutely agree with you, slang is part of the language and should be learned but it is something that you pick up over time and should only be used in informal situations like text-messaging or daily conversation. In summary, Portuguese is a beautiful language and should be appreciated. It is not a difficult language, as many Brazilians like to say, the thing is that people don't take time to really understand it.

Alice, thanks for your comment. You really understood what I meant. And it's a pleasure to read a text so well done like yours. thanks again.