Well after 24 hours no response, looks like this forum is not very active. I have found the manuals but still I can't change the language of management console.
Sorry for late.
Manual: have you try to search via Google "teamviewer manual". This is in the very first result https://www.teamviewer.com/it/support/documents/
Translate: your language has been determinated via regional information transmitted by your browser.
Welcome to the TeamViewer Community!
You can change the display language of the Management Console on the sign-in page: https://login.teamviewer.com
At the bottom of that page, you will find a drop-down menu from which you can select your preferred language.
I hope this helps.
All the best,
... information is saved by cookie.
If you configure your browser to clear the cache on exit, you will lose this information and you will need to reset it.
The type combo always report, without cookies, the value derived via regional.
If the request is to change the language with automatic mechanism, you must set an alternative language for the browser and configure it as default. Access OAuth, then do not allow the passage described (?correct?): you must set the language directly on the user.