Something is corrupted and I don’t know what it is

You see i have this Lenovo ThinkPad T420. Everything was well before and i dont really wanna go in complet detail. Basically there was a virus and the laptop was resseted. Usually the laptop would have no problem in windows 10 but then suddenly after the incident it has been acting strange. It is a bit slow and whenever i restart it just shuts down. Please help I’ve been trying to do this for nearly a month now. I just want my T420 back 🙁