Heya Deathbringer96!
Let's try to figure this one out together, it could be caused by a bunch of different things.
Could you try these things:
1. Make sure you don't have any mods enabled
2. In Steam, right click the game, select Properties -> General -> Launch Options and check that it is empty
3. Rename your "Documents\Paradox Interactive\Crusader Kings III"-folder so a new one is generated
If everything above fails:
1. Right click the game on Steam -> Manage -> Browse local files
2. Delete everything inside the Crusader Kings III installation folder
3. In Steam, right click the game ->Properties -> Local Files -> Verify integrity of game files
This will reinstall the whole game.
Please report back after you've tried out these steps!