Why does Paul Baumer try to help the French soldier

Paul feels a closer kinship with the enemy than he does most other people. He feels like the French soldier could have been a brother to him. He feels a crushing amount of guilt for killing the French soldier. He vows to help his wife and family.

Paul also feels that the French man may very well had been him. He sees the French man as an ordinary person. When he leaves the shellhole, he completely forgets about the French man.