Complex sentence: Caroline Müller was Sweden's leading opera prima donna after Elisabeth Olin, was after her retirement replaced as such by Jeanette Wässelius, and she was director of the theatre school during a period of expansion and development in this school's history.
Split into simpler sentences: Caroline Müller was Sweden's leading opera prima donna after Elisabeth Olin and was after her retirement replaced as such by Jeanette Wässelius. She was director of the theatre school during a period of expansion and development in this school's history.