First, I sense that you should keep work on improving your mastery of English grammar. I have a few resources for that:
* Technical Writing One by Google [1] is a pretty good self-study course for practicing the fundamentals of writing mechanics.
* Find some kind of program that forces you to write and get feedback on your writing. English classes at community colleges, for example. There are probably a lot of online resources, too. The best way to improve your writing is to practice and get feedback; just like the best way to learn about programming is to create programs.
* A Writer's Reference [2] is a canonical reference text for looking up grammar rules.
I know this is boring work but it really is the foundation of communicating clearly.
After you've got those fundamentals down, you'll want to learn about the processes that technical writers follow to figure out what docs customers really need. Docs For Developers [3] is a pretty solid overview of the process that many TWs follow.
[1] https://developers.google.com/tech-writing/one
[2] https://www.amazon.com/Writers-Reference-Diana-Hacker/dp/131...
[3] https://www.amazon.com/Docs-Developers-Engineers-Technical-W...
https://www.amazon.com/Docs-Developers-Engineers-Technical-W...
I'm think I could do with reading that. As could the team I'm on.