I'd like to learn

[Vipershark]

What do you mean it won't let you copy?
Are you using the selection tool beforehand?


Okay, I went through and cleaned up a few things, particularly the top of the hat, the nose, and a little on the ear. (Mine is on the right)
It's not perfect, but this is the type of thing you want to do. Look at your reference and try to follow the curves and proportions.
I removed the shading for now since there's not much use in shading if your lineart isn't ready but that will go back in next.

So from here, go through your sprite and do your best to clean up the lineart and make it accurate to the reference I posted above. There are several areas that you want to look at in particular, such as the shoes, the gloves, the buttons on the suspenders, and the mustache.
Also, if you compare the sprite to the ref, Mario's head is too far down and to the left and is sort of resting on his shoulder rather than in the middle where it should be.