It's easier to cover-up your own lack of clear thinking, by using complex sentences and long words. You can easily deceive yourself. So I try to be concise, in the hope of clarifying my own thoughts. I suppose you can express your thoughts clearly and concisely in your own language, otherwise you wouldn't be asking; I just wanted to note that it's not necessarily a matter of foreign languages.
I don't know how old you are, nor what is your station in life, nor what kind of English you want to speak. Are you a techie? A writer? If you aren't hitched, get a native boyfriend/girlfriend that is interested in the field you want to be competent in. Everyone I know that is really fluent in {$FOREIGN} has, or had, a {$FOREIGN} partner.
Hell, just hire someone with the right competencies, to be your companion for a few months.