There are 3 keys to improving on and writing a good story that I think everyone should know. And its stuff I've had to work on and improve on and am still working on and improving on.. and one of the reason why my older stories are very cringe looking.. but my more closer to present year ones actually feel like they weren't written by a 12 year old lmao.
1. Prose: Always work on your prose.. always make sure you're not writing an essay but are using language that grips- but not overusing it. Re-read each paragraph and see if you actually enjoyed reading it, if you didn't, if it gives you a headache .. you might want to rethink it.
2. Read.. TONS of books.. and I don't mean fanfics on Wattpad.. Fanfics tend to be a mixed bag quality wise- even mine- and it won't give you a good standard for what qualifies as good writing. Read real novels, and spread out your genres, even ones you don't usually read or like.. read Dickens, read Tolkien, read Rowling (who despite being a bigott, does hold good examples of prose and building up tension- along with how to write slice of life situations). Read Lovecraft (also a bigott), read Stephen King, Hell, read Christopher Pauloni, he wrote Eragon at 15, if anyone can show you how well a young person can write, he can. Diversify! Read a bunch of Star Wars Legends novel if you like! Manga doesn't count, I love manga and its beautiful art- but it can only teach you how to write dialogue overall.
3. You won't always know what happens in your story. You can have a framework.. I want character to develop this way by the end, they start out like this, they fight this at some point, and then the ending is this- that can be your skeleton- but when you write, you're reading it too (That's the fun part). Write like this, and you might surprise yourself and you won't feel bored writing long chapters either. Its Daydreaming by writing.