Complex sentence: In the late 1980s, he raced the BMW 320i Turbo, BMW M1 Procar with his son, Walter, winning the domestic in 1990 with his Porsche 935 K3 and competed in the Interserie with a Porsche 962.
Split into simpler sentences: In the late 1980s, he raced the BMW 320i Turbo and the BMW M1 Procar with his son, Walter. As well, he won the domestic in 1990 with his Porsche 935 K3 and competed in the Interserie with a Porsche 962.