Complex sentence: Three years later, Ma Kwun (Donnie Yen), a police officer from another precinct, is assigned to replace Chan, who is going to retire soon, and take over leadership of Chan's team, composed of Wah, Sum and Lok.
Split into simpler sentences: Three years later, Ma Kwun (Donnie Yen), a police officer from another precinct, is assigned to replace Chan, who is going to retire soon. Ma will lead Chan's team, composed of Wah, Sum and Lok.