I would say that the brain doesn´t learn by seeing
(I understood you - by studying/by being in touch, etc) either one or the other way.
Learning English, to my thinking, is a bit on the active/interactive side, so just reading or going to an English course won´t do, it takes some use of the language, some exercising your skills (the sum of several skills).
Obviously, there are cases and cases, one may or may not have the resources, time, money etc to invest in education, so he/she will go for the easiest route , but one should - if possible to get their skills in use, or they may get rusty! Again, it´s just my opinion here, others may think in different ways.
At this juncture, being an intermediary level student would be good to see your English here. It would be a way to keep learning new things, correcting others and one way of putting your head and time where your brain is (paraphrasing the "put your money where your mouth is).
Feel free to make follow-up questions, we of the EE will be happy to answer them and help you out.
By the way, by degrees, we need to "unglue" from Portuguese a bit, after some time of studying English. Back to the crux of the matter, it´s not about learning PT-EN or EN-PT is being in touch with the English language all the time (or whenever possible).