In the camps, Wiesel must struggle to stay alive and to remain human. How well does he succeed with his struggles?

There are two parts to the question.  The first part is
how well Elizer fares in the struggle to stay alive.  The answer is that he does succeed
in this quest.  This is proven by the fact he is alive at the end of the narrative.  The
second part is naturally a bit more complex.  The notion of "remaining human" is
something whose definition changes over the course of the work.  It might be difficult
to suggest that he remains human by the end of the work because of the amount of changes
he undergoes throughout the course of the work.  For example, the typically human
experiences of collectivity through community, connection with family, and faith in
divinity are all repudiated throughout the course of the novel.  It is not as if Eliezer
chose to sever these bonds, but rather such choices were made for him, removing him from
specific aspects of his humanity.  In the end, when he stares at the mirror and is
unable to recognize the face staring back at him, it is because his humanity has been
robbed from him.  I am slightly bothered by saying that he "failed" at his struggle to
remain human because of this precise lack of autonomy.