The main idea/important event in Gn 9 is that God makes a promise with man; that allows them to accept their mistakes and to have a second chance. The first thing that happens is that God blesses Noah and his sons with a covenant saying that there will no longer be any floods that destroy humanity. He tells them that he will mark the clouds with a bow (rainbow) to show us that he is keeping his promise. Noah plants a vineyard and he gets drunk because of the wine. He then gets naked outside his tent. Noah tells his sons that they shouldn’t live their life without giving other people second chances
" I will establish my covenant with you, that never again shall all creatures be destroyed by the waters of a flood; there shall not be not be another flood to devastate the earth" (Gn 9: 11).
"I set my bow in the clouds to serve as a sign of the covenant between me and the earth. When I bring clouds over the earth, and the bow appears in the clouds, I will remember my covenant between me and you and every living creature-every mortal being-so that the waters will never again become a flood to destroy every mortal being" (Gn 9:13-15).
"When Noah woke up from his wine and learned what his youngest son had done to him, he said: 'Cursed be Caanan! The lowest of slaves shall he be to his brothers.' He also said: 'Blesses be the Lord, the God of Shem! Let Caanan be his slave. May god expand Japheth, and may he dwell among the tents of Shem; and let Caanan be his slave'" (Gn 9:24-27).
Everyone deserves a second chance because everyone makes mistakes.