I'm going to show you a very useful website that all the English learners must know, it is EnglishExperts.
I recommend this website because there you, Portuguese native speaker, can find many tips, grammar, podcasts and articles. Thy also have amazing e-books, that are very good, have good quality and low price.
If you want to take a look at the English Experts E-Books store, click here.
I really hope you love it as I do!