The wording of the question is an interesting one. I am not entirely sure that Bruno has any agenda that requires "support" or "assistance." It is this purity that makes his befriending of Shmuel so transparent and so transcendental in a world that is far from it. He simply follows the end of a fence and then finds Shmuel there. After talking, both of them recognize how "boring" Auschwitz is. Their friendship arises out of a general need for companionship. When Shmuel is abused by the guard in the kitchen of the house, Bruno does not say anything. Perhaps, this is motivation for him assisting Shmuel to find his family in the camp, causing him to burrow under the fence. Yet, I think that his overall friendship with Shmuel is not driven by a need for support or assistance in terms of some specific agenda or end. Rather, I simply think that the two boys struck up the purest of friendship in a setting where purity was lacking in many.