Complex sentence: Like most navies the German Navy had never before used twin-turrets for such small guns, all previous designs were made for 8-inch guns or larger and were to heavy for a 6000-tons cruiser as allowed by the Treaty.
Split into simpler sentences: Like most navies, the German navy had never before used twin-turrets for such small guns. All previous designs were for 8-inch or larger guns and were too heavy for a 6000-ton cruiser as allowed by the Treaty.