It's no problem at all, friend! Don't worry about it!
I am using Winrar and just for visual aid I guess, this is what I'm getting.
Oh it worked. What the heck?
I added this Game as a Non-Steam-Game on to my Steam Deck. It will get an Steam Library Id if you start it trough Steam so you shouldn't get this error.
Bugs where they appear for no reason and then go away for no reason are always so weird...