Why is learning English difficult for you?

English is a language that I always liked but I not learned to speak as well as I want because this I am here in the United States studying to improve my skills with the language. I have still some difficulties, as refer to listening. Some times I do not understand everything I hear in English, for a few reasons such as many words I do not even know, in some situations people talk too fast and I cannot keep up due to some idioms used commonly, but in English course I had done so far I have not seen these typical phrases of those who live here, besides the accent that some people have, then the pronunciation of words vary greatly depending on the region the person is. Another difficulty concerns speaking. Often I end up changing the words in time to talk, just as I have difficulty in formulating the sentenses, in the other words, I change sometimes the place each word in the correct order, so sometimes by the time I'll end up putting words I speak has nothing to do with the sense I wanted to say, and end up talking too slowly, because it's like my brain is transferring and organizing the words to speak, and often the words disappear and happens like a blockage in the brain and I can not express myself properly. Another difficulty is the writing. Related to writing, the limitations are similar to those of speaking, but as I have more time to write than speak, is easier to organize the ideas and words, unlike speaking, when you have to express what you want to convey at the time, then ends up being more complicated for me. Finally, despite my difficulties in listening, speaking and writing, I'm still really enjoying English and my goal is to return to Brazil totally fluent, so I will continue studying a lot and I will study further, and watch movies and videos in English, talk to people from other country to to force the practice of language, besides read more articles and books to develop my skills with the language.