If you want to know how to go from fanfic writer to pro writer, this video has some great pointers. How To Go From Fanfic Writer to Pro Writer – YouTube Video https://www.youtube.com/watch?v=Emh0XkzCzYs (about 29:52 minutes long).
In the show more section of the video link, there are some links to other things, like
Bad Fanfic Writing Habits You Need to Break: https://youtu.be/SmbUAKi-ovY
What Fanfic Can Teach You About Writing: https://youtu.be/gG-LpRqIlYM
How to Achieve Good Story Pacing: https://youtu.be/OMyY6bDp67s
Intro to Story Beats (Save the Cat): https://youtu.be/Kp7NR2cmSS4
There are a number of other links that I didn’t include above, but you may want to check out.