Hello, @natalie.bannert . . . saying “yes” or “no” when he is asking you something is not one of the things his language update will understand. Here is the complete list of German commands and questions you can ask, but the responses to those questions he asks you need to be in English.
Also, in English, you need to speak distinctly and somewhat slowly. You can get EMO to understand your English better by submitting your voice here.
Also, let us know how it goes and if he has caught up with his age yet.