Guru replies in the language of your most recent message. You don't need to set anything: write or speak in the language you want, and the Guru follows.
How it works
It follows your latest message. If you switch from English to French part-way through, the next reply is entirely in French. The Guru doesn't mix languages in one reply.
British English is the fallback. If the Guru can't tell which language you're using, for example because your message is very short, it replies in British English.
Activities follow too. Quizzes, role-plays, deep dives, skill review levels and role-play feedback are created in the language of your last message.
Knowledge is translated for you. If the Guru's content is in another language, the Guru translates the relevant facts into your language when it answers.
For example: a store assistant in Lyon can ask "Comment gérer un client mécontent ?" and get the answer, and a quiz on handling complaints, in French, even if the Guru's training content is in English.
What uses your profile language
The Guru's buttons and labels, such as Get Started on a quiz card, and the two suggested starters on your first visit, use your profile language. So if your profile is in English and you chat in French, the Guru's replies and quiz questions are in French but the buttons stay in English.
In voice mode, the greeting uses the language of your last typed message, or your profile language if you haven't chatted yet. After that, the Guru replies in whichever language you last spoke.
For creators
For YouTube videos added to a Guru's knowledge, HowNow uses the video's English transcript, so a video without English captions may add nothing. Uploaded files and web pages in other languages can still be used.