Travel by Car: The driving distance between Duisburg and Mostar following fastest route is 1.630 km, and estimated travel time is around 15 hours. Recommended route goes trough Croatia, Slovenia, Austria via highway where tool fees apply. In Germany highways are free of charge.
Travel by Bus: If there are direct buses from Duisburg to Mostar, timetable and price tickets you can check here. Alternatively it is also possible to travel via Sarajevo or Split in Croatia.
Alternative ways of travelling from Duisburg to Mostar:
Travel by train: It is possible to travel by train, but in total travelling time will be much longer compared to travel by car or bus. Trains in Bosnia and Herzegovina and in Croatia are very slow. If you decide to travel by train, first from Mostar you have to travel to Zagreb (via Sarajevo). From Zagreb there is an international train to Germany. More information for travelling by train in Bosnia and Herzegovina you can check here.
Travel by plane: There is no direct flight, but there is option to fly from Split to Cologne in Germany. Distance from Cologne to Duisburg is 85 km.
Map with buses from Mostar: