Complex sentence: On the day of the contest Gayathri and her team are shocked that the song which they have composed was stolen by other troop and she misunderstands that Kannan has stolen and sold their work for money despite Kannan's protest that he is innocent.
Split into simpler sentences: On the day of the contest, Gayathri and her team are shocked to learn that the song which they have composed was stolen by the other troop. She assumes that Kannan has stolen and sold their work for money despite Kannan's protest that he is innocent.