Complex sentence: Early in his career, Syberg began to paint watercolours, becoming one of Denmark's masters and completing a whole series of paintings when in Pisa with his family from 1910 to 1913.
Split into simpler sentences: Early in his career, Syberg began to paint watercolours, developing into one of Denmark's masters. He completed a whole series of watercolours when in Pisa with his family from 1910 to 1913.