So i made a better tutorial. because someone on steam told me that he had the same problem.
So what you want to do is: Delete the local contant with steam. Just delete the game. Than go to your C:\Program Files (x86)\Steam\steamapps\common and delete the Ylands map if its still there. Than you go to %appdata% Just place it were C:\Program Files (x86)\Steam\steamapps\common <-- is standing and press enter. search for the Ylands maps and stuff delete those.
The next thing you do is
start regedit. you just typ in the search balk of your windows "regedit" en press enter. Export your regedit for safty, make a backup. And than you also search the ylands regs with Ctrl + F and typ ylands and delete every register from ylands and save. Now you can install ylands again and it should work, well it did for me!