what is responsible for designing it?
The ships were ordered as a reply to the Royal Navy's three new s
Derfflinger-class battlecruiser
The ships were ordered for the 1912–13 Naval Building Program of the German Imperial Navy as a reply to the Royal Navy's three new s that had been launched a few years earlier. 
what is derfflinger-class battlecruiser? A class of three battlecruisers
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Derfflinger-class battlecruiser [SEP] Introduction
The "Derfflinger" class was a class of three battlecruisers () of the Imperial German Navy. The ships were ordered for the 1912–13 Naval Building Program of the German Imperial Navy as a reply to the Royal Navy's three new s that had been launched a few years earlier. The preceding and the incrementally improved represented the end of the evolution of Germany's first generation of battlecruisers. The "Derfflinger" class had considerable improvements, including a larger primary armament, all of which was mounted on the centerline. The ships were also larger than the preceding classes. The "Derfflinger" class used a similar propulsion system, and as a result of the increased displacement were slightly slower.