Sorry, but I very much doubt that you're going to get it anywhere near perfect from the state it is now. You could follow some of Souly's advice without having to re-draw the entire piece, but, it's not going to change much.
In my opinion, I say you should forget about the competition, concerning this particular piece, at least, and continue working on this at your own leisure, following the good critiques given to you. You can do a much better job when you aren't so limited and can take any advice in open arms. Then, eventually, you'll get good and fast enough, that these competitions won't be as hard and limiting.
For actual critique, your colors are way too saturated.. They seem like MS Paint default colors, with (a lot of) llighter/darker shades.
There is no form or sense of volume to many things, and look rather flat. (and blobbly, like someone has pointed out.) You can fix that by adjusting your highlights and shadows, as well as your colors.
