My challenges learning English

Hello to all who read me!
Finding in my last year of undergraduate study within the university, one of the great challenges I currently have is learning English.
My educational training on learning English has been quite problematic. The truth is that at the school where I come from, I had several problems in learning the language. This product of the instability that had the permanence of the teachers who taught English in the school. Every time a teacher came, he was soon fired. This was because he had irregularities in learning English. To this is added for not being self-taught in my training during my school stage, which intensifies my problems of learning the language.
Actually, learn English is a necessity in today's academic world. Unfortunately, English has become the main language for reading, and entering the academy. Today, most of the publications in scientific journals are in English. So if I want to meddle in that world, I must learn English.
One of the main things I have about English is to be able to internalize the language. When I study, and I'm with English classes, I don't have any more problems with the language. The problem arises that all that knowledge is usually lost over time. So I have trouble retaining everything I have learned.
Today, I am committed to being able to learn the language, so I will continue to look for some methods to be able to speak and read English fluently. I hope I can do it.
Thanks for reading, and I hope they are well by the contingency