I was losing 40-50 fps before, but then I discovered the was because I didn't have protontricks configured, watch this vid to see how to do it: https://www.youtube.com/watch?v=Habh5Tf5fCs .Not my vid btw, but it helped a lot, also DON'T try to change the -dx12 command line on steam to -vulkan, that's how I was losing fps if it doesn't open that's because you haven't configured proton tricks yet or your drivers are out dated, for me it was both