Additional settings-related features and issues within Microsoft Teams for business
Hello Mario,
Good day!
I'm Jericho, a fellow customer and an individual advisor. I am happy to assist you!
With regards to your concern, apologies but certain features to add multiple languages at the same time in Teams is not yet possible. You could only select one language for both keyboard and app language.
I may suggest that you reach out directly to Teams UserVoice feedback hub and raise this concern as to let the devs know about this feature and they'll be able to look unto this concern. See link below.
https://microsoftteams.uservoice.com/
Hope that helps! Please let me know if you have other queries/concerns.