Before you add the files to the locale folder, you must remove the resource name. (e.g. from qb-drugs-de.lua to de.lua). Further you have to change the language file in the file fxmanifest.lua (e.g. from locales/en.lua to locales/de.lua). Some words or texts you have to translate yourself, because they can be in other files like (e.g. in index.html or in main.lua of client and server ). Have fun!