Translation not complete. We are using xwiki 9.11.3 community edition on Debian 9. Our wiki needs a complete localization in German language. Many parts of the translation are still with English terms.
I could not find documentation on how to make custom add-ons to the localization. In older posts an applications_de.properties was mentioned. But this file doesn’t seem to exist anymore.
How can we expand in a custom way the localization of our xwiki installation?
So there is several aspects here.
If you find missing translation it would be great to contribute them on http://l10n.xwiki.org/ 
Everything contributed there end up in next version.
Then while waiting for the next version (or before contributing them 
) the simplest is usually to put missing translations in a document with object XWiki.TranslationDocumentClass. See http://extensions.xwiki.org/xwiki/bin/view/Extension/Localization/#HRegisterawikitranslation for more details.
It was ApplicationResources_de.properties and it did not changed, there is just more of those now (it used to only be located in oldcore jar).
Note to self: We need to reduce the duplication. Both versions have info that the other version doesn’t have
Thanks for the quick answers. We try our luck with the TranslationDocumentClass (and as needed possibly the other hints as well).