I would suggest three things (apart from the obvious 'speak in english with others'):

#1 read english books. translate every unknown word from dictionary. the words improve vocabulary; the sentences improves grammar.

#2 watch english movies with english subtitles. this helps greatly in understanding the accent. plus english in movies is a hell lot easier than the one in books.

#3 talk to yourself in english. there was a period in my life where all my thoughts were in english. it makes you comfortable with the new language.

ps: these are just general points - your english is pretty good!