Wow, this is a toubled sprite. When I saw it I first thought you were using wide pixels, due to the accidental wide frontal and back views. Then, realizing it is square pixels I zoomed in and at first thought you had stretched it using smoothing interpolation by accident, something I wouldn't put past a coder, since it's not their field. But I . . . ok wait a minute, I just opened yer sprite sheet in Photoshop and you did smooth stretch it, it has over 256 colors. Haha. oy.
Yeah, well, I hope you saved a version before you stretched it, otherwise it's back to the drawing board.
Moral of the story - you're over your head and have much "studying" to do. Even concerning basic technical graphical issues.