I've recently installed pocketmine and I'm having some issues with the world generation. My world is clearly not a classic minecraft 1.11.3 world and is some custom generated mess, with the looks of an alpha pe edition world or something. I've played around with the settings in the server.properties file and the pocketmine.yml, both of which I've had no luck even after deleting and remaking the world so I am currently a bit stuck. Any help would be greatly appreciated, thanks!
PocketMine has bit outdated generator... You can try find some plugins for better generators like a BetterGen by Ad or something like this.
Probably yes, it was possible (I think that newer worlds haven't loading)... However you can transfer java edition worlds.