Sometimes configuration files are locked. Right-click the steam_emu.ini file, go to Properties , uncheck Read-only , and hit apply before editing.
This steam_emu.ini method is widely referenced. For instance, on F1 22 , the language can be changed in both game settings and the flt.ini file (FLT being another crack group's emulator). Other users on discussion forums have pointed out that games like Dying Light use a steam_emu.ini where you can change the language line.
Here’s exactly what worked for me (and it took less than a minute):