FYI: ctrl + shift + t brings back closed tabs.

Use a hex editor to read binary files. I recommend ImHex https://imhex.werwolv.net/ because it includes all sorts of advanced analysis stuff.

Now my question is, how should I deal with these pacnew files?

Install pacman-contrib which includes pacdiff. Meld is easy for beginners.

DIFFPROG="meld" pacdiff --sudo

See https://wiki.archlinux.org/title/Pacnew_files#Managing_.pac*_files for more options.

AFAIK you can skip the “download” by also copying the corresponding .acf file in the parent directory.

Steam starts Proton inside a container and runtime. Maybe those provide some special $stuff for those games.