Complex sentence: Manfred Fischer was CEO of Gruner + Jahr until 1981 when he was promoted to the board of Bertelsmann, their parent company; he was replaced by Gerd Schulte-Hillen.
Split into simpler sentences: Manfred Fischer was CEO of Gruner + Jahr until 1981 when he was promoted to the board of Bertelsmann, their parent company. He was replaced by Gerd Schulte-Hillen.