100% gpu

Hello, I am speaking to you here because I have had a problem with my PC for several months, this problem generally occurs after several hours of use. When this happens, my clock at the bottom right of my screen freezes and it is no longer possible to perform any actions on the operating system...

Please help me! I have a 2 year old HP Omen 17inch 1080 resolution screen with a NVIDIA GeForce GTX 1070, i7-6700HQ Processor, 8GB Memory, Windows 10 home. I have DirectX12. Everything runs smoothly, all except my frame rates per second in games. Everytime I load a game - Assassin's Creed...