Nice starter tree, Amur maples are famous for being winter hardy and fast growing. Great where trident maples are not quite winter hardy.
Everything Osoyoung said is on the mark. I would add that you seem to have a knot of branches all coming out of the trunk at the same point. In time this will cause swelling and a zone of reverse taper. If it were my tree I would prune off all but 2, I would probably keep the smallest of the branches plus the tall leader to continue the thickening of the main trunk. Amur maples bud back well so hopefully new branches will appear more spread out over more of the trunk in places where you want them.