First, make sure to not run steam in administrator mode.
To ensure this, go to steam's install directory (by default:C:\Program Files (x86)\Steam)
or steam's desktop shortcut,
right click on steam.exe , hit properties , go to compatibility tab and make sure that the
"Run this program as an administrator" is NOT ticked.

Afterwards, go here
https://community.pcgamingwiki.com/files/file/1873-unifairysys-denial-for-mihoyo-games/
and download the batchfile.
Run that as administrator and when the command prompt pops up, hit 1 on your keyboard.
That's it , now just open up your game & Enjoy.

If you ever wanna uninstall HI3 it's suggested to run the batch file again and go with 2nd option this time , to remove Unifairy.sys entirely from your system (haven't tested this yet)

Happy mashing