Need help with my overheating laptop

So my Asus Nitro laptop keeps overheating and shutting down and I have cleaned all the fans, and repasted the thermal paste. When the CPU reaches around 80-90C it completely malfunctions the screen turns greenish and just stops working and I don’t understand why. When I changed the thermal paste the temperature of the cpu didn’t change at all still 80-90C and shutting down. I may think it’s a bad heatsink but I’m really not an expert with laptops.