I am sure that you have heard of that saying "PRACTICE MAKES PERFECT." In other words, the more you do something, the better you become. So speak English as often as you can. Do NOT worry about "mistakes." Ask your native-speaking friends to correct ONLY the big mistakes. There is no magic in learning languages. If you use it a lot, you eventually WILL learn it. Millions of people have come to the United States without knowing much or any English. If they continue to speak it every day in everyday experiences (work, friendships. travel, etc.), they eventually come to speak and understand it very well.

Improve by communicating in English with people as much as you can. Also you could skype me and i could help you out and tell you how to improve.