The prologue's lines foreshadow the story's main plot: a tragedy between star crossed lovers. It revolves mainly around civil blood and how it will make the civil hands' unclean which is the main 'clue' of the ending of the story which is death.
Hope this helps!
Answer: They want to help the missionary, J. Everett Grimes, who is in Africa working with this tribe. The blacks are a poor people in need of help as long as they are in Africa and not next door. Harper Lee puts this scene in the story to show the hypocrisy of these women.
That's actually perfect! For someone who claims they're not good in English, you're on a roll! Keep up the good work (: Good luck!