dlibra in Poznan is in the process of electronically disseminating German Casualty lists from WW1. As of this writing, the library has published dozens of documents from the years of 1914, 1915 and 1918. You may find the complete lists (as they are updated) on the Wielkopolska Biblioteka Cyfrowa site.
Note: These lists are neither digitally indexed nor searchable. In order to find those you seek, you will need to read the lists ‘manually’.
If you wish to search more broadly for German War Casualties, you might try the Kriegsgräberfürsorge Gräbersuche-Online.