Yamaha MG10XU with Cubase LE AI Elements 9.5 Audio setup question.

First off this is my first mixer so these maybe some stupid questions. I am using a Yamaha MG10XU and Cubase AI 9.5. I use the mixer to adjust vocals and for FX while streaming video games through OBS. I have everything setup and working. What I’m wondering is first how can I make it where I don’t hear my voice in my headset? Because if I use the mute button or turn the volume off then I cant hear my game. Second is when I speak and record my pc sounds plays through my mic as well. Which is normally not a problem except when I speak in Discord to other people. They hear may pc sounds/game when I speak. I dont know if there is a way to setup something in Cubase to fix this. Or I may have to run my headset through my pc sound card and then mic through the MG10XU. ???