[MM3-users] not correct language in subject(s)

When receiving all types of system mails from mailman3 (3.3.8) there are almost all the subjects in English, althought text is in German. Am I missing somehting?

The option to have the list in german is toggled and so far all the mails are in german ... also templates on different levels work fine, either en or de, but obviously the subjects are not translated (?) or taken from an English template.

Any hint is appreciated, regards, Jens.