To display the date in the German language, you need to follow these steps:
- Set the site language in Admin dashboard > Settings > General > Site language: German
- Set the timestamp to true
- Use the function date_i18n() and follow the documentation to output the localization date. https://docs.metabox.io/fields/date/#template-usage
It might be complicated for the beginner but Meta Box is a developer tool, it helps you to output the raw value. So you need to have a basic knowledge of coding to display the value in any way you want.