When you start the level, you will be right under a thwump, so get out of the way, jump on it, and let it carry you to the top. Jump to the second opening and hold the left arrow key so you don't go at full speed. Jump towards the switch, land on the slide, and let it carry you down. Now go back to the left and jump into the other slide. Jump up the slope and get the switch. Go back down, use the thwump to carry you up again, and quickly go across the gaps to reach the door switch. Fall into the first opening you come to, and move to the exit.