Hooboy. The mechanics of this chapter were OK.
But the characterizations and plot are simple, juvenile, and not at all original to HP fanfic. If you were a ninth grader, this would make sense and we would expect you to get better with more reading and life experience. If you really are 20, then perhaps you should find some great stories and reread them with an eye to how the author transfered his tale to paper.
Maybe buy and memorize a copy of Writing and Thinking by Foerster and Steadman.