From the Super Mario Wiki, the Mario encyclopedia
The level layout is similar to Level 5-DK, though with shorter conveyor belts and Bob-omb Blocks positioned over a pit of spikes. Falling onto the spikes will result in Mario instantly losing a life. Donkey Kong will send out Bob-ombs that the player needs to pick up and throw back at him. Donkey Kong also has a Direction Switch that he will use to change the direction the conveyor belts will move in. When Donkey Kong takes three hits, he will send out four Bob-ombs at once. Hitting Donkey Kong once more will defeat him, and the player can move on to Twilight City Plus.