Complex sentence: On top of that he had a form of virtuosity in all kinds of dance, which he used with the finest taste, and his favourite student and dancing partner in Sweden was Charlotte Slottsberg, with whom he made a successful pair in the ballets.
Split into simpler sentences: On top of that he had a form of virtuosity in all kinds of dance, which he used with the finest taste. His favourite student and dancing partner in Sweden was Charlotte Slottsberg, with whom he made a successful pair in the ballets.