Good evening Michaela and welcome to the Events Calendar Support forum!
Thank you for reaching out to us.
I would love to help you with this topic.
As it turns out, the Events Calendar Pro is already translated in German for the most part.
You can see that here: http://translations.theeventscalendar.com/projects/tribe-events-calendar-pro
Normally, if you have the latest version of all of the language files it should go well.
As a first troubleshooting step, could you please provide us with your complete system information in a private reply using the instructions found in the following link?
https://theeventscalendar.com/knowledgebase/sharing-sys-info/
Best regards,
Geoff B.