Looks like in Germany you do need an IDP or a certified translation of your licence. from their Transport ministry.
"If you hold an International Driving Permit, you do not have to have it translated.
You must carry a translation of your domestic driving licence if
it was not issued in a Member State of the European Union (EU) or a state party to the Agreement on the European Economic Area (EEA) (Iceland, Liechtenstein, Norway), or
it is not in the German language, or
it does not comply with the provisions of the Convention on Road Traffic of 8 November 1968 (Annex 6). You can find out whether your driving licence complies with the provisions of Annex 6 by enquiring at the appropriate authorities of the issuing state."
These pages provide information on the most important German provisions for holders of foreign driving licences. If you have any further questions, for instance about the procedure for registration and issuing of German driving licences, you should contact your local driver licensing authority...
www.bmvi.de