What are the essential writing skills for creating novels and short stories? How can one improve these skills?

I only recommend three skills to become a successful writer of novels or short stories:

Reading: Yes, reading is a skill you definitely need if you want to be successful as a writer. Think of it like, If you want to be a great basketball player, you'd watch lots of games and study the moves of the pros, right? Reading novels is kind of like that. You're learning from the best and seeing how they do it.

English And Vocabulary: Of course, you’re going to write it in English if you want it to be successful and if you’re not a native, or you’re english’s not good, then you’ll probably get stuck on minor things or sentences that makes sense in English but don’t in your language. That’s why practice as much as you can and improve your vocabulary.

Storytelling: If you think you can’t do that, then quit your idea of writing a novel becaus you can’t be successful if you don’t have that rhythm of storytelling. But who said there’s not a solution to that the solution to that is:

……………………………………………………………..“LEARN”

And that’s the answer to, how you can improve your skills