Game Not Starting At All

Hi, I've just finished the game and was about to do the DLC, but when I tried to play the game on Steam, it just didn't work. It says it's running, and it is, but only as a background process. Help me, please. I've been really excited for the DLC, and now I can't play it.

Game only running in the background

Steam says its running

If anyone knows a solution, I would be EXTREMELY grateful!