How can I make Google Now talk back in other languages than English? My brother is getting gradually blind from diabetes and I want to help him setting up his phone (Samsung S6) with Google Now so he can voice-control it.

Apparently Google Now can only talk back if you set the voice language to English only. In Danish, everything is half-baked. For example, with English as the only language enabled in Now, I can say "What time is it?" and have Now speak the time. If I add Danish, it still understands the command, but it just shows a google search with "What time is it". It doesn't matter if I ask in Danish or English, it just performs the search.

Likewise, with English only, I can say: "Please text Michelle" and it will respond "What's the message?". I then say the message and it will ask if I want to send it now or change it etc. In other words, you can have a dialogue with Google Now.

Not so if I enable Danish. I can still say "Please text Michelle" (or the corresponding phrase in Danish) and it will prepare a message. But I will have to enter it manually and then press send. I cannot continue with voice commands.

My brother has no problems interacting with the phone in English, but without adding Danish to the voice language, he will have to stick to English text messages to all his friends and acquaintances which seems pretty awkward. Also, without Danish, it is almost impossible to ask questions involving Danish place names, like "What's the weather in Århus".

Is there a way I can make Google Now understand Danish without loosing functionality?
Firstly, my best wishes for your brother. 

As for your question. My phone is in English. But I set the Google Now to understand both English and Turkish. Please note, Google Now itself is in English. But it understands Turkish commands too. I believe the very same can be done with Danish as well.

At Google Now, go to:


Settings
Voice
Languages


From there, choose Danish.

In my phone it looks like this: Default Primary: English(US) Others: Türkçe(Türkiye)

P.S: Google Now decides what language it should be based on your phones language settings. So in order to make the app in English, your phone too must be in English. Since your brother has no problems with that, I don't think that'd be a problem.