Oh you make me remember ny first time writing. I don't know if you should listen to my advice, since I'm the kind of writers who love to plan. I plan the characters, the plot before writing. I love connecting events that happen in my stories. And once you start writing and you know your characters well, things will just happen. Like some times my characters just do what they want hahaha
And the best advice to improve your writing (except for writing itself) is reading.
Good luck, dear

I remember the first time when I started writing fanfics and I was doubting whether I would ever get some readers or comments. I totally can relate to you but you don't have to be afraid! If you think your ideas are interesting, start planning and writing the draft. Along the way, you'll see the improvements in your writing skills and really, there's no right or wrong ways when it comes to writing.

I suggest you to start try writing mini paragraphs for the ideas that you wish to publish and this can contain the main plot of the entire story. From there, you can start building the sub-plots and characters.

I believe you can do well ! I wish you all the best with your first fanfic ♡

Well my suggestion is, write it down! It doesn't matter if it's terrible, you'll improve with time! But if you don't write it, you'll never improve ^^ all of us start somewhere so do write it down! Fightiiinngg