I think it's all about practice. If you want to improve your writing, start writing down your thoughts as a blog post, for instance. Maybe even here on dev.to? There are a bunch of free web tools, that will analyze your writing and tell you how you did. Have a look at hemingwayapp or grammarly. These tools help a lot!
Regarding communication in general, I highly recommend the book Soft Skills: The software developer's life manual by John Sonmez and my blog programmergoals.com. ;) It generally covers the topic soft skills for software developers. And just last week I was at the Microsoft Tech Summit in Frankfurt where I met Shayne Boyer (Microsoft Developer Advocate) among others and he also emphasized the importance of communication and how you can practice it.
Check out this short YouTube video I did with him (more are coming soon!)
Hope this helps!
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