It’s not uncommon for an organization to want to provide services in multiple languages. While Teams auto attendants and call queues each have a language setting, you can only set one language for each call queue or auto attendant.
About Call Queues and Languages
While call queues do have a language that you can set, there isn’t yet much that can take advantage of the language setting – text to speech greetings and voicemail transcription at this point. Interestingly, every language I selected could handle both that language and English, however pronunciation of words that exist in both languages was done according to the language selector. It may seem like a great cheat to configure your call queue for a non-English language (French, for example) and then have it handle both English and French duties, however this can lead to unintended outcomes. Aviation is spelled the same in English and French, however the pronunciations are quite different!

The solution here is straightforward – create one call queue per language and assign users as agents in the appropriate call queue(s). Set the language on each call queue appropriately.
About Auto Attendants and Languages
Auto attendants have a variety of prompts and greetings, as well as voice input instead of keypad input. Mixing languages within one auto attendant would be a mess for pronunciation, prompts, and speech enablement for call flow options (dos vs two vs deux for the default of speaking the option number). The solution is to have one auto attendant for each language, especially since the call flow may be different for each language. That does lead to the problem of how to get callers to the appropriate auto attendant for their language.
The non-technical solution is to have completely separate auto attendants, each with their own phone number. Your website, marketing, etc., can indicate which phone number should be called for service in each language. In situations where you need a caller to choose their language, I recommend the following two solutions:
Two or Three Languages
In your auto attendant for your main language, record a greeting such as “Welcome to Contoso. Pour un service en français, appuyez sur un. Para servicio en español, presione dos. For sales, press three. For support, press four. For our location and hours of operation, press five.” Have option 1 send the caller to a French auto attendant and have option 2 send the caller to a Spanish call queue.
I specifically say here to record a greeting. The text-to-speech option would use the language the auto attendant is configured for, in this case English. Having the English auto attendant try to read French and Spanish will sound terrible. You could try to bodge things into place with interesting spelling, but it’ll still sound terrible. Find one or more people in your office who speak the other languages well and have them record the entire greeting (if possible) or just their portion of the greeting if not. You might also try Azure Cognitive Services Speech to generate the greeting segments in each language, edit them together, and upload that.
Four or More Language
If you have more than two or three languages, you’ll burn through the quantity of call handling options just in redirecting callers to their preferred language. If you have 4 languages and 8 menu options, you’re out of luck for doing that within one auto attendant. Changing your menu options will also quickly become a nightmare of greeting audio file recording and editing. Instead, create an auto attendant that is solely to direct the caller to the auto attendant that’s in their preferred language, and build one auto attendant for each language.
Editing Greeting Recordings
And finally, if you’re looking for a excellent (and free!) tool for recording and editing your greeting recordings, I recommend Audacity. While there is WAY more functionality in Audacity than you require, it is amazingly capable of editing your files, as well as exporting them to a variety of different file types. Help and support is excellent, and given the popularity of Audacity, you’ll very likely find what you’re after with a quick Internet search.