Please strengthen your English Grammar and vocabulary first. Then read some good papers, especially written by natives. Read your paper twice or thrice, you will improve English of your documents yourself and you will feel it. Then hand over to your colleague good in English for revising the document. Then you will feel that now it is in very good shape. Just observe each time the corrections.
See e.g. the book Science Research Writing for Non-Native Speakers of English ( http://www.amazon.com/gp/product/184816310X/ ) by Hilary Glasman-Deal and the links below