Can't Exit Full Screen

So I was in the options menu, and i accidentaly hit the fullscreen mode. For some reason, it slowed my game down to a crawl. So much in fact, that it takes about 3-5 minutes just for the game to sense my cursor over a button, and another 3-5 minutes for that button to load up, etc. So I eventually got to the options menu, clicked on the button to exit fullscreen, and it still stays in fullscreen. I restart my computer, and the problem persists. I REALLY need help. Should I uninstall Beamng, or is there another method? Thanks

P.S. The alt+enter hot key does not work

 

id say redownload.