Press the green flag, then do the various tasks needed to progress. The first task is the statue asking you what the password is. Look in the top left corner of the gray room to see the password. The second task is the maze game. Get to the red border on the right side of the screen. After the maze game, Prof. Mubble will ask you math questions. Answer then correctly. After that, you will battle Malfoy to get your broomstick back. Hold down the space key. PS: Please do report any glitches to me.
There is one glitch left in the game I cannot figure out how to fix. It's at Malfoy's battle. The backdrops keep switching. I'll make a separate game for the Malfoy battle.