First, open the Creative Cloud desktop app, click on the gear icon and choose Preferences > Creative Cloud. Change the language to English.
Now uninstall Indesign and reinstall it, using the CC desktop app,
InDesign uses, if different languages are installed the primary language of your OS if available. Either change your OS to German or uninstall InDesign and install the English version only. You have to change the language in the CC desktop application before installing.