Windows menu, configuration, then click "Security & Updates", in that menu click "Restore", you will see two options, pick the upper one (Restore this PC). Then follow the asistant. Do a backup of everything you want to be saved, ETS2/ATS savegame is not linked to Steam Cloud, so I'd recommend to save it apart.
If this doesn't help, I'd recommend you to go to a PC repair center on your city.
Good Luck!
and sorry for late answer