100% of 1 Pros
Practice. I would invest in Grammarly.com as a tool that helps in real-time. You can use it to correct and give you suggestions on your grammar, whether you are texting, emailing, typing a letter, filling in comments on websites.
Second the advice to read a lot of books. Try reading a book and listening to the audio-version at the same time, to understand the pronunciation, syntax and grammar.