You know that tired adage “write what you know”?
It’s utter crap. Forget it.
At the very least, outgrow it.
Write what you want to know.
Confront the questions and puzzles and secrets and I-wonder-hows and what-ifs that itch at the back of your brain late at night, and make up the answers. Just make them up. Then write the living fuck out of them.