there are many ways to improve it. you can improve your English by watching a movie once and once again until you've already learnt at least the 90% of the new vocabulary talked by the characters during the movie, also by talking to others who speak or learn English, by writing on websites like this and being corrected by native English speakers or teachers and by reading books or magazines.... particularly I used to watch movies and animes in English, try it if you want, it's really useful...

The best way to learn any language is to speak it! Even if you don't know it very well. Talk to someone who speaks the language you're learning but not the language you know. It can be very difficult and sometimes frustrating at first but you will be amazed how much you will improve.