One of the best ways to write English better is to READ, READ. and READ English.

I can tell

I'm (has to have an apostrophe to replace the unused letter in the contraction) not good at writing. (Peirod, Snetence Break) I always make spelling mistake, (comma) so plz(this is acceptable on the interenet, but the actual word is please) teach (not "to") me how, so that I can rise my self from that kind of problem.

Start with very simple sentences that are correct and build from there. Pay attention to word order. e.g. I saw you. I saw you yesterday. I saw you with your dog yesterday. etc, etc. Also learn "chunks of words". e.g. "safe and sound", "no idea at all", "absolutely no idea", etc etc.