I got made fun of as a child by a parent for doing art and just... never did any ever afterwards. I primarily hang around artists tho and would like to relate to them more, but none of them do creative writing. I've read numerous grammar books, so that won't be a problem, but none really go in to how to construct a sentence, paragraph, page, chapter, plot, etc. I'll happily take any advice on the subject, really anything you can think for someone with actually zero experience.
Good advice I've gotten so far is to just write basically whatever. Also, people who are visual artists and creative writers, which was "easier" for you to become fluent?
Stephen King wrote "On Writing" about his process, might be worth looking up.
Grammar is iffy. English has so many contradictory rules, trying to approach it from a formal rules based prospective is very difficult.
King and I both agree on "just write whatever". You might try picking a writer you like and re-writing part of their work. Try out different word choices, try to mix it up. Let their writing be a framework for you to play in and see what you can come up with.
You're already making coherent posts that clearly communicate your question and the context in which you're asking that question. You're starting from a good place.