The complexity of video game graphics and their user interface elements has grown exponentially. So, to make the gaming experience more comfortable and convenient, most gaming platforms support a long list of languages. Like others, you can change the game language in GOG Galaxy as well.
Please note that some titles have language settings available in the in-game options menu. As such, you can only change languages for GOG games and not for others. Also, if you see the Manage Installation setting grayed out with the message "Managed in-game only", it means you can only change the language from the in-game menu.
GOGUnlocked offers free GOG games. It allows you to play games without the need for activation keys or cracks. It's not exactly illegal, but there are certain situations in which it might be. It is safe to use. There are no viruses. Each game comes directly from GOG.com, which is a simple installer and directly playable via the desktop shortcut.