An easy way of doing this is to read children's books, however stupid it may sound, they are designed for children learning the language and could be a good way of learning better sentence structures. Try to begin with the basics, full stops,capital letters,general word order; then progress onto more complex structure involving semi-colons, 'exotic' conjunctions. And I'm sure your writing will become more eloquent and sophisticated, although it really just requires a bit of practice. I hope I could help.

Can I give you one very small suggestion? It's a tiny thing that will make your written language look so much better, and give a much more positive impression to whoever reads it. Always remember to start your sentences with a capital letter, and always write the pronoun 'I' with a capital letter. Not hard, is it?