This has an interesting plot idea to it, and despite this fanfiction being your first one it is not too bad. Yes it is a little rough around the edges with some of the grammar and spelling, but overall I was able to follow along well with what was happening,

I would highly recommend you check out the writing guide on this website, I am sure you will find it useful.

And do not forget to preview any future chapters, so you can fix things like double spaces and big spaces between paragraphs.