Well, I have finished reading what you have written so far. A few things strike me immediately. You're very imaginative. You have a good plot and you write with a clear passion for your story. What is holding you back? Poor grammar usage. You use is, was, were, where, and misuse words often. If you're using Microsoft Word 2003 to write, I would suggest that you Start at the beginning of your chapter and scroll through it. Anything underlined in green is word misuse. Your verb usage would also be consistent with english not being your primary language. I would highly suggest getting someone to beta for you. If you do not know what that is I will tell you. Have someone online read your story and check for, and correct, errors before submitting it.
Lastly, I hate the Harry/Ginny pairing but that is a personal choice for me. Had to through that in.
Geovanni Luciano