I'm a newbie , but I install steam from flathub and works perfectly
flatpak install flathub com.valvesoftware.Steam com.valvesoftware.Steam.CompatibilityTool.Proton com.valvesoftware.Steam.Utility.protontricks

Very appreciate the help of every of you! Even though pretty much nothing has worked out, I'm still feeling support and I'm not alone with the problem =)

As for @kaktuspalme and @Staudey I didn't try your tips yet, I can only test those later.

Thank you, everyone!

    decembre-dhiver I think your problem is or was probably a multipart problem. The last one with Dead Cells I'm pretty sure is a problem with libbsd as I could reproduce on my system as well. But it should be fixed with the current update thanks to @Staudey
    But Nvidia Prime might also have been a problem.