Flicker of Mist and Fire (The Elder Scrolls 5: Skyrim)

Hello. I played Skyrim for a long time, but recently abandoned it. Launched in a month and the fog and fire began to flicker. Also, the fog sometimes becomes a different color (pink, yellow, etc.). I searched the Internet for a long time, but I did not find anything. Tried reinstalling but didn't help. Also, when launching the launcher, the graphics were automatically set to Medium, but now they are set to Low. The computer is ancient, but Skyrim has always pulled. Please help.