Complex sentence: He took on the mantle of director, directing "Naanu Nanna Kanasu", his directorial debut ever in Kannada in 2010 for which he was the joint producer and the film completed 125 days successfully in the theatres across Karnataka becoming the biggest hit of the year.
Split into simpler sentences: He took on the mantle of director with "Naanu Nanna Kanasu" in Kannada in 2010 for which he was the joint producer. The film completed 125 days successfully in the theatres across Karnataka becoming the biggest hit of the year.