Complex sentence: In 1987 he was promoted to Co-General Manager of the comapany and in 1988 he became General Manager, in 1994 he was again promoted to Managing Director and in 2001 he assumed the responsibility of chief executive officer.
Split into simpler sentences: In 1987 he was promoted to Co-General Manager of the company, and in 1988 he became General Manager. In 1994 he was again promoted to Managing Director, and in 2001 he assumed the responsibility of chief executive officer.