You have been speaking (or at least trying to) speak English for the past 14-15 years of your life and your current level of language proficiency is an accumulative reflection of that. Truth is, two short and intense years in a Junior College will not magically improve your language. What you can do, however, is to 1.) minimize your mistakes, 2.) ensure clear and accurate expression and 3.) build up your vocabulary (both academic and general).
In a valiant (and hopefully not futile) effort to address (1), this page will contain a list of common mistakes that you seriously need to avoid (for both my sanity and yours). I will continue to update it so do check back often.