Complex sentence: The upper wing was significantly longer broader and thicker than the lower and was in three parts, with a rectangular central portion that was mounted over the fuselage on two outward-leaning streamlined steel struts from the upper fuselage on each side.
Split into simpler sentences: The upper wing was significantly longer broader and thicker than the lower and was in three parts. The central, rectangular portion was mounted over the fuselage by two outward-leaning streamlined steel struts from the upper fuselage on each side.