drops to 3-8fps in fullscreen, on a gsync monitor this is crippling

I had played The Raintime previously, but Steam gave me a missing file error when I tried to run the game today. I even uninstalled the game, deleted the game folder, and redownloaded, but it just downloaded an empty folder. Does anyone else have the same issue? Maybe it's an issue with my Linux install, but it worked on my machine before....