Why does elizer give his father marching lessons?

Eliezer gives his father marching lessons to help him maintain his strength and stamina during their time in the concentration camp. The lessons serve as a way to keep his father motivated and to instill a sense of discipline in a situation where their lives are increasingly chaotic and dehumanizing. By reinforcing the importance of marching correctly, Eliezer hopes to protect his father from being singled out by the guards and to improve their chances of survival. Ultimately, it reflects Eliezer's deep care and concern for his father amidst the horrors they face.