You can only end the rental in the same country that the vehicle was initially rented. Either within the service region of a particular city where SIXT share operates, at a hvv switch point within the Hamburg service region, or at a SIXT station. You must make sure that the vehicle is properly parked in a designated parking space on a public road where parking is permitted for a 48-hour period in accordance with road traffic regulations. The rental vehicle may not be left in parking zones with parking discs or in resident parking spaces.
If you’d like to return your car to a SIXT share station, you can find more information here.