Complex sentence: The first Porsche 718 was an open-cockpit racing car built by Porsche in the late 1950s and a successor to the legendary 550 Spyder, represented the highest level of the four-cylinder flat engine.
Split into simpler sentences: The first Porsche 718 was an open-cockpit racing car built by Porsche in the late 1950s and a successor to the legendary 550 Spyder. The 718 represented the highest level of the four-cylinder flat engine.