1. Choose English you want to learn and stick to it: American, British, South African, Australian... It is very important. Do not mix it.

2. Learn the sounds of that English very well. Sounds, the correct pronunciation is key.

I have not learnt that way. Unfortunately. None of my former teachers had said that I should have focused on sounds, pronunciation at first place. Also, I had not any idea about that. I thought I would work on my pronunciation, accent later. Now is the "later" and I have problems. My pronunciation is strong, I mispronounced words, my speech is not always clear, and it seems I have to re-learn many words.

Maybe in one or two years I will start to learn another language. When it happens I will definitely start with the sounds of that language. I will not care if it takes 3 or 6 months.

Assiste filmes americanos com legenda dupla. Acho que isso vai ser uma boa ajuda pra voce se acostumar com o idioma.

First, you need to define your terms. Do you mean "fast" as in days on the calendar, or hours of study time?

Thank you very much for help me!

Yes, I agree with Peter. I am re-learning my pronunciations that many words I pronounce them incorrectly from the scratch by guessing their pronunciations without looking up with dictionary. Also, my local common mistakes when pronouncing some words.