for context I had this same issue on windows and got frustrated from it so I switched back to cachy and I still have the same problem so maybe this might be an issue with my computer. I tried deleting and reinstalling steam and that didn’t work also another issue I have is that steam will crash randomly.
We do not discuss pirated software here.
As for your “taskbar is not going away” problem: are you sure your games run in fullscreen? Which Desktop Environment do you use? Can you provide a screenshot?
Also some panels have options like “Pinned” or “Above all windows” .. in Plasma it has Visibility > Windows go below.