First off, we don't know, if he is really stubborn - sometimes horses seem lazy and stubborn, but in fact they are confused and/or scared, and their way of saying it is refusing to move or seemingly paying no attention to cues. Also, it can be related to health issues or not being able to carry out the worload he's asked to. And, as the horse is very young, he might need a more experienced rider to set all the cues very clear to him, just as you should take lessons on a more experienced horse, so that you don't teach your horse unwanted behaviors or make him sour. There's not much else to suggest, just get a competent trainer from your area and find a riding school for yourself. You and your horse will both be better off that way.
I have come a long way, to surrender my shadow to the shadow of my horse.