To beat the fire monster, switch to Hermonie and have the Glacius spell equipped. When the monster shoots its arms at you and they hit the ground, Freeze it and then when the fire is out, Flipendo it until it disappears. Do this to the other arm too. Then when it opens it's mouth, shoot glacius into it. When it shuts its mouth, back away because it explodes. Do this 3 times, I think. Then you won!!!!!!!!!!!!!