What is the significance of the scene in which Paul returns home for a military leave? What do civilians know about the war?

The civilians know nothing about the war. They are full of conjectures and misinformation. Paul is a changed person. He has little in common with the people he grew up with.

Paul discovers that he is completely disconnected with the people he was formerly close to. His mother is ill; the people in the village only know what someone like Paul would tell them after coming from the front. He lies to Kemmerich's mother about the young soldier's death; he finds that the civilians are starving. There is no home for Paul anymore so he again feels displaced and estranged from everything.