@crimson_moon__7 not an expert but I will would write down all your ideas, plots and scenes— everything you got inside your head dump them all. And also don't worry if the sentences are small, because our brains turn editor mode before we write down the first draft. . . And it's okay if it doesn't make sense, make sure the idea you want is written or basically gossip to yourself in your notes like.
Example from ATG
Let's say you wanna write a scene where eunha making Heeseung jealous or just piss him off. But the sentence doesn't make sense but you know what you want.
Simple write under your sentence with a bracket. (Eunha basically makes Heeseung piss of, by going to the dancing floor with Kaya, with their hands wrapped around each other and they kiss to piss both Jake and Heeseung off)
Okay lol I hope this make sense but you just gotta have notes for yourself like this sentence I want to have this tone and meaning.
And your sentences or the chapter will come out very clearly once you like to understand or know your characters and the direction you're going with.
Hope this helps ༎ຶ‿༎ຶ idk even know whether this is the help you wanted or not but yeah