Read a lot!! You will pick up reading, and should get more literary experience and see different techniques which should help with the writing too! I would also recommend writing a lot. Whether it is stories, fan fictions, poems, or whatever just write. You will get better with time. Also just pay attention and be creative with your ideas.
Research, practice, and ask grammar questions. Make a reading schedule to help you read frequently. Write every day for, say, 20-45 minutes. If you don't have time for that, bring a notebook around and write during your free time. Hope this helps!!
Play games like: monopoly, win, loose or draw, password, pictionary and so on. And read books that interest you and challenge yourself with harder and harder books to read. With writing, start a diary, get a pen pal, try to write for your school newspaper.