Arduino Code explanation

I have a arduino sketch. I want someone to put detailed comments on each line explaining what is happening at that line of code. The comments could be as long as it could be to make me understand what is happening. I am new to arduino and I have to modify this sketch to add more functionality to it to make a project as a part of my job. I am learning so do not know much about nuances of how it works. The sketch is for a Robot movement. It is a Robot with 4 mecanum wheels, Arduino Mega, Ethernet Shield, 2 Kangaroo motion controllers, 2 sabertooth motor controllers, 4 dc motors with encoders, 2 12 volts lead acid batteries. the motors runs on 24 volts dc. There is a separate desktop software installed on windows computer to control the robot. Let me know if any more information is required. The sketch is about 570 lines long.