heikoT

Problem:
WordPress displays the German language by default informally using the default locale de_DE.

How to display German in formal language? ("Sie" instead of "Du")

Solution:
To use formal German in WordPress please go to WPML > Languages > Edit Languages and use the following locale (Default locale) for German:

de_DE-formal

Then go to Dashboard > Updates and download the latest translations from WordPress.

Relevant Documentation:
https://wpml.org/documentation/getting-started-guide/language-setup/editing-wpmls-languages-table/#adding-your-own-languages-using-wpmls-gui