Not understanding grammar or punctuation doesn't give you a free pass to avoid writing. As I've said, writing in simple forms can get you started in your mission to learn grammar. But don't stop there. As time goes by, you should improve your knowledge. Here are a few simple ways to develop your writing skills.
1) Write your own material as much as possible. Avoid using your administrative assistant as a crutch.
2) Read as little as 15 minutes a day. Choose wisely, for example, a modern, noted author. When you read, analyze the usage of grammar and punctuation that scares you. Look up words you don't know.
3) Avoid texting abbreviations when possible. When you write an email, don't write: "u 2." Spell it out and explain.
4) God and Word gave us spell-check. Use it.
5) The Internet is a wonderful research tool. Look up usages about which you are unclear.