Hello @anon54216031,
welcome to the Asana Community Forum 
Normally the notifications and the language within Asana desktop and other versions such as mobile should always be in the language of the user (from their phone for example).
See an explanation here for example: How to change the language in app - #9 by Marie
In case that does not help I recommend reaching out to support as I am sure they‘ll be able in having this resolved.