the update made the game run at 15 - 25 fps and is impossible to play
Go to Settings and turn your quality down the the lowest one. By default, the quality is medium now, and the realtime shadows are a bit worse for performance. If you set your graphics to the lowest, though, it will disable all realtime shadows which should boost your FPS. I was able to get the game to run at a smooth 60 FPS on my crappy laptop by lowering the quality and the resolution.
Downloading the game will also increase your framerate, and if you download you can set a downscaled resolution to make it run smoother.