The short answer
The CALC interface is available in 17 languages: English, German, French, Spanish, Italian, Dutch, Czech, Slovak, Polish, Turkish, Portuguese, Russian, Ukrainian, Chinese, Japanese, Korean, and Hindi. Mia answers in the language of your conversation, whatever the interface language. PDF reports are created in the language of your conversation, but not every script can be shown in the PDF yet.
Interface and answers
You change the interface language with Language in the sidebar. The answers follow the language you write in: ask in German and you get German, whatever the interface says.
Standard and National Annex
The chat language does not determine the project country or the National Annex. Tell Mia which standard and National Annex apply to your project.
PDF reports
A report is written in the language of your conversation. You do not choose a separate report language.
Latin scripts, including diacritics, and Chinese appear correctly in the PDF. Korean, Russian, Ukrainian, and Hindi characters cannot be shown in the PDF yet, and Japanese is only partly supported. For these languages, read the results in the chat for now.