To change your language, either for your server, or for yourself, its quite simple. All you need to do is run the language command with a valid ISO code. If you are the guild owner, the command will automatically change the server wide preferences, but if you are just a member of the server, then it will change your specific user preferences. Specific user language preferences, if they exists, will override server language preferences. You can change your language to any valid ISO 639-1 Code that is currently supported by the bot developer. As in, only if the code provided is a valid code that also exists in the bot developers message.json file.