The pilot and co-pilot are supposed to be working in tandem during the decent and final approach. The co-pilot is supposed to be doing continuous call-outs (air speed, altitude, etc.) and literally puts their hands on the controls if the pilot isn't following strict procedures.
You couldn't be more wrong if you'd tried.
In the airline world, their is no such thing as a "pilot" or "copilot".
We call them "Captain" and "First Officer" and they trade off roles as the "pilot flying" (PF) & "pilot not flying" (PNF).
Their roles and duties are interchangeable on each flight (at most airlines). So if the First Officer was acting as the PF during this flight while going through training, the Captainis ultimately responsible for the safety of that flight.
Their is no "taking over" of controls. The one thing you are correct about is that they are supposed to work as a team. The rest is patently false.
