Hello,

Please install the German langauge packs for core and then addons see:

https://www.jevents.net/download-area/translation/category/jevents-core-translations
https://www.jevents.net/download-area/translation/category/club-addons-translations

Note make sure to install the same one as the Joomla! German language pack you have, i.e. de-DE

Many thanks
Tony