> Eg I tried saying in English “I don’t understand” (even though I know how to say that in Spanish) and it responded in Spanish which may be hard for absolute beginners.

I tried to use ChatGPT as a "live" translator with my in laws and I noticed it is extremely bad at language "consistency" or at understanding your intent when it comes to multiple languages.

It will sometimes respond in English when you talk to it in the foreign language, it will sometimes assume that a clear instruction like "repeat the last sentence" needs to be translated, etc.

I don't know how the person above is approaching the problem but your experience is consistent with mine and I don't think GenAI models (at least OpenAI ones) are suitable for the task.