Complex sentence: He began his career as a film director with the National Film Board of Canada and in the US where he made television dramas and was a partner in a film company with Anthony Shaffer for 13 years.
Split into simpler sentences: He began his career as a film director with the National Film Board of Canada and then worked in the U.S., where he made television dramas. He was a partner in a film company with Anthony Shaffer for 13 years.