Complex sentence: There were plans to fit four anti-aircraft guns, but only two (former anti-tank guns scrounged from the army) could be acquired and were installed on "Kormoran" s superstructure behind sheet metal panels.
Split into simpler sentences: There were plans to fit four anti-aircraft guns, but only two (former anti-tank guns scrounged from the army) could be acquired. These were installed on "Kormoran" s superstructure, and were hidden by sheet metal panels.