A. Death says this. It is the last line in the novel. THis is after Liesel's life story is complete. It reflects the paradox Death constantly finds in humanity. He loathes them and is enchanted by them.
B. Death is talking again. He is narrating to us. This is in the first chapter. He is musing about how it's harder for the living losing a loved one than the dead.
C. This is Max when he is young. I believe it is a flashback. It is a relief when Max fights death. He had witnessed his uncle die without a murmur. Max decided that he would never die without a fight, "When death captures me, he will feel my fist on his face." Death comments that it likes that "stupid gallantry." In this section Death feels the satisfaction of a human life not willing to let go. Death notes that God had not given him any respite and not taking a soul felt serine. This is ironic because taking souls is what Death does. Certainly leaving them is not in his job description.