Why did again make the part1and part6 parallel?

I'm going with your second question here. Arrival has to do with the arrival of immigrants and their experiences. The man has no real knowledge of others in similar situations to his own until he meets a group of refugees, who tell him of their stories of escape from war, genocide and violence in their homelands. He also meets other immigrants like himself who are still able to live or exist in their old countries, but who were able to see that the situations there would likely degenerate very quickly.