The writing expression can only be improved by writing on daily basis on any topic that interests you then get it checked from any of your friends who you feel is good at English Grammar.After that, write again on the same topic but this time you should avoid repeating same mistakes you did in your first draft.This practice of writing should not be for oneday or two but until you have reached your destination.With the passage of time, you will feel that your expression has improved dramatically and obviously you will have proud on hard work you did, energy you put into it.New writers always have peculiar fright that their abilities will be judged on their writing but this fear lacks solid footings.Everyone makes mistakes in the beginning.No one was born with such an eloquence style of writing;all have achieved with the practice and their efforts.So start writing and keep writing.