Update:
My game was running on 22fps max even in a new map. I deleted everything. The game folder and the profile folder in appdata. Did a reinstall of my graphicscard drivers (first used AMD Cleaner to remove everything). Now i'm getting 34.8 fps on a very large map. 15 cities, 60 factories.
Yeah i don't get those youtuber fps.... 5700xt isn't the best card, but absolutely not the worst!