Massive Framerate Drops

Necroposting, but anyways.
The game worked nice for a month or so, and then fps started to drop drastically when moving - to 10-20 fps. Sometimes earlier the game lagged a few first minutes and then smoothened. But now it's constant. Restarted the game, reinstalled the game, updated video driver - nothing.

Tried both steam and normal version (steam version freezes when I go to desktop).

Many someone will find a solution.