The-witcher-3-wild-hunt-game-of-the-year-edition-gog-language-packs
Click on the game to see the "Extras" or "Backup Offline Installers" section.
You can manage your language settings through the GOG Galaxy client or via the GOG website: : Go to your Library and select the game. Click the Customization button (next to the "Play" button). Select Manage installation → Configure . Click on the game to see the "Extras"
If you only need to change subtitles or text, check the → Language menu within the game itself. Available Language Support Click on the game to see the "Extras"
: English, Polish, German, French, Russian, Portuguese-Brazil, and Japanese. Click on the game to see the "Extras"
You can select your desired language from a dropdown menu to download the full installation files in that specific language. :
Wild Hunt Game of the year edition - German language pack | Forums