Complex sentence: Romana continued to work closely and extensively with Joseph Pilates learning the method until his death in 1968 then continued working with Clara Pilates for another 11 years until her death in 1979.
Split into simpler sentences: Romana continued to work closely and extensively with Joseph Pilates learning the method until his death in 1968. She then continued working with Clara Pilates for another 11 years until her death in 1979.