I am learning German now and i know English also. For me its easier to write in German. In Inglish some many words have no sense how are they written. In German u write jist like as u speak it. U just need to know some rules and u are ready. Read more or practice it by writing the same things you speak on German. When you are not sure how its written, check it and correct it if its wrong. I personally use ditcc.com for searching for a word or checking gender and phrases. Probably that you will need to learn again the basic rules like why it is written spazieren and not spaziren for example.