Permission to operate a motor vehicle in Germany is regulated by a number of different factors depending on where your license was issued. Please see the following website for detailed information:
Federal Ministry of Transport and Digital Infrastructure
International Driving Permits may be used in Germany for up to six months. For some countries, you will also need to carry with you an official translation of your license. If you have an International Driving Permit, you do not need to have it translated.
If your license was issued outside of the EU or EEA and you plan to stay in Germany for longer than six months, you will need to get a German driving license in order to continue driving here. Different rules apply for converting your current license to a German one. In some cases you may need to take a driving test; in other cases, you may need to take driving classes; and in still other cases your license may be accepted and converted as is. Details about converting (umschreiben) a driving license (Führerschein) can be provided by the citizens’ office (Bürgeramt) of the City of Frankfurt. It is a good idea to inform yourself about these requirements well in advance.
To have a driving license converted, you need to make an appointment with the citizens’ office and show up in person to submit the application.