Games for SteamOS are not PLUG&PLAY:

WALANG SUPPORT ANG SETUP NG GAMES SA STEAMOS! There is not guarantee that all games are compatible with it. THIS IS NOT A PLUG & PLAY SETUP. There's an extra steps to setup before you will be able to run the games since it is a Linux-based Operating System.

You need to adjust Proton Settings, Compatibility Settings, Add the .exe file as a non-steam game, use thrid-party app such as Lutris, Lossless Scaling, etc.

SET UP ON YOUR OWN RISK!

IF YOU UNDERSTAND THIS, YOU CAN NOW PROCEED.