Hi,
there are German language packs available. They contain the translation for the OOTB Aras elements and ensure that your users get the correct date and time format for their region.
Make sure to select the correct one that fits your Innovator version. If possible, test them in a test environment first. Once you enabled an additional language, you cannot remove it anymore.
https://www.aras.com/de-de/support/downloads/language-packs-hotfixes/language-packs/germanlanguagepack
link
In general the German language packs have good quality (I use it by myself). But they sometimes "over translate" things, which means Aras literally translate everything, even administration elements not relevant for the end user. This is a bit inconvenient when you admin team uses the German browser language as well.
For custom ItemTypes, properties, etc. you have to ensure to provide the proper translations by yourself.
Regarding documentation there is not much German content available, but the browser translator most of the time does a good job.
Best regards
Angela