Customizing foreign language event confirmation email
For information about how CiviCRM handles languages, see https://lab.civicrm.org/development-team/translations/wikis/home  

Text strings in the templates are wrapped in {ts} ... {/ts} tags - that is what triggers the translation.

You could customise the German translation, or if your confirmations are only being sent in German, you could customise the confirmation message itself directly in German - see https://docs.civicrm.org/user/en/latest/email/message-templates/