helloo! sorry for tha late response, when I was first writing the fanfictions I would take inspiration on other authors and their styles and create my own. what also helps is a self study in english writing, it can help you with grammar and transition words and such. they have books on here that help writers in that department when they are stuck as well!
as for making your story go viral, it took time for my story to gain recognition, mostly because my first fanfic was up since 2017 and had gone through a rewriting three years ago. just give it time and you’ll see many supporters and readers making a new discovery in your works!