Changing the language to German is unavailable in QuickBooks Online. Here's the list of available language:
English
Chinese
French
Italian
Spanish
I recommend sending feedback about language options. Please click on the Gear icon and select Feedback.
Don't hesitate to post in the Community if you have any concerns.
You are leaving Intuit.
You have clicked a link to a site outside of the QuickBooks or ProFile Communities. By clicking "Continue", you will leave the community and be taken to that site instead.