Hello Nikola! Glad you decided to re-sign in into your account. The forums are a nice place to hang out!
As for your question, I think the Fan Fiction and Writing section is actually the place you're looking for. You don't need to write a fiction per se, but there's a prefix named [Pokémon World] there, which I think is made for the sort of thing you're creating:
https://www.pokecommunity.com/forumdisplay.php?f=20&prefixid=poke_world
You can check other threads with this prefix to see if it's indeed the type of thing you're doing. I hope this helped!
See you around!