1. First learn to understand English
English is not learned by speaking, but by listening. Focus 80% of your studies on learning to understand spoken English and only 20% on learning to speak English, which I guarantee will be difficult if you fail to learn to speak English. This is exactly how we learn our native language, this is how we learn English when traveling to England, for example, and this is exactly how we should learn the English language.
2. Vocabulary first
When learning new words and phrases in English, what matters are the meanings of those words and phrases, not the rules for how or when to use them. The meaning of a word or phrase will always be the most important fact, as it is what will allow us to both understand and communicate in English. One example of this is that learners who have a lot of vocabulary but little grammar often do better than those who know a lot of grammar and have little vocabulary.
3. Grammar is for reference only
Grammar is just a way to clear up doubts arising from our studies and clarify phrases that we currently don't understand. However, just as no one learns Portuguese through grammar, you will not learn English by studying grammar. Use grammar as a reference, but not as your main way of studying English.
4. Regularity in studies
Don’t get carried away by talk of traditional “intensive courses”. Studying English is a long-term undertaking, which requires regularity rather than intensity. Always study every day, even if it's just a few minutes, because each day you study is an additional step towards victory in your studies!
5. You are responsible for your learning
You will never learn English by being a passive student and waiting for someone to teach you the language. In the same way that your parents didn't teach you Portuguese (you learned it), no one can teach you English. Books will help a lot, but you will always be responsible for your learning.
6. Learning English is much simpler than it seems
The English language is one of the easiest languages on the planet, as well as being much, much simpler than Portuguese. If you were able to learn the Portuguese language, you can certainly learn English, just use the correct techniques. Don't think that people who know English are smarter than you, I assure you that this is not true. With time and persistence, you will discover that the English language is much simpler than it seems.
7. There is no ideal age or “gift” for learning the English language
It doesn't matter if you are 15, 30 or 60 years old; There is no right age to learn the English language. Anyone of any age can learn English if they use the right methods, just as anyone at any age will not learn the English language if they use the wrong methods. Likewise, there is no “way” to learn English. At first, certain students may find it a little easier due to personal characteristics, however the ability to learn foreign languages is the same for everyone.