Central eMail Advanced Quarantine Summary emails in other languages than english

The language of the Digest is setup by creation of the account, which was likely english in your case.

You can request the change to another language via Support Case. 

Thank You LuCar Toni,
which Account do You mean? The Central Account of the customer or the personal account of the customer user to access  the self service portal?

The entire central tenant. Central can only use one language for the entire account, so multi language reflection is not possible - You can use English or an alternative language for the entire account. 

Sorry I am a bit confused.
When I set up a new monthly customer account in central partner dashboard, there is no option field to select a language for the new tenant account. When I launch the new created customer, I see all in english. In this context I can chance the language of the super user but not of the tenant. Where can I see the active tenant language in the partner and/or the customer central dashboard ?

Could be the case, that for a MSP Account, it is always english. I am just aware of the situation, when you setup an account via Trial it can be an alternative Language. 

As said, you can let this changed for your tenant by raising a Case.

OK, that was the answer I was looking for. Thank You!