My games are freezing

Hello all,

I recently bought Imac 27 inch with 5K (2017), because I wanted to play some pc games which were not compatible with Mac OS, I used the bootcamp (Windows 10 pro). However, games are freezing while I play the games; Overwatch, League of Legends. I use mid settings with 2K resolution on games which I get 144+ fps, but they are randomly freeze and unavailable close them, I have to log out or restart the mac. I have never had this problem with my Macbook Pro. Please help me out.

My imac specs are:

CPU: I5-7500

RAM: 16GB 2400 MHz DDR4

GPU: Radeon Pro 570 with 4GB memory