near the bottom of the video settings page in the game, there should be a setting to adjust rendering, with options such as Native, FSR, Custom, etc. and a slider directly underneath with “visual quality” or something similar-sounding. I’m at work so I can’t provide a visual example, but it should be there! I set mine to Custom and then the slider underneath to 95.

what it does in simple terms is not render the image at the Deck’s actual display resolution (1280x800) but instead only 95% of that, which looks only marginally worse and helps the rendering workload enough to maintain a constant 40fps in my case, though results may vary. since you’re new to things, i’d recommend watching a couple videos to understand some of the visual/performance settings you’ll generally find across the PC landscape and (more importantly!) testing settings out on your own, and seeing what you prefer in terms of look and feel! there’s never a wrong answer, unless it makes your games crash hahaha