good story so far but you have many mistakes in spelling and especially in grammar...you should really work on punctuation as well. commas are useful when speaking...just thought you'd ought to know...
overall, I'd say your descriptions of battles, character looks (Tonks when she met Harry), and sex (though, I must admit, I laughed at that little side note) are rather lacking but, with all the other stories I've seen, you're much better off than some....a few others are just atrocious... -__-;;
you have a good concept going but I must say you really jump a lot in the story...now I'm not expecting a long novel or anything but make a story too choppy and people may start to lose interest...some of the conversations, especially the ones involving Dumbledore, were rather confusing in some areas...not sure if it was from what was said or how something was said but it just confused me.
anyway, hopefully this review will help a little. (I've heard a lot of authors say they want some blunt "constructive criticism" reviews but....) well, looking forward to your next chapter!