Complex sentence: In 1978, Stempel became General Manager of the Pontiac division and in 1980, he became Managing Director of Adam Opel AG, the German subsidiary of GM. In 1982, he became General Manager of Chevrolet.
Split into simpler sentences: In 1978, Stempel became General Manager of the Pontiac division. In 1980, he became Managing Director of Adam Opel AG, the German subsidiary of GM. In 1982, he became General Manager of Chevrolet.