If you are using manual files or community fixes, they generally need to be placed in the following directory: Steamapps\common\SniperGhostWarrior2\Game\languages\
If you have a physical disc or a version from a different launcher that lacks language options, you will need to search for a "Sniper Ghost Warrior 2 English Language Pack" zip file. These are commonly hosted on community forums or game fix sites. Sniper Ghost Warrior 2 English Language Pack Download