Jonah told the people that if they didn't stop their bad ways in 40 days, everything in Nineveh would be destroyed.
Stop doing bad things or in forty days the city and everything in it will be destroyed.
The king heard what was going on and ordered everyone to stop doing bad things.
Jonah left the Nineveh mad because wanted the people to be punished for their bad ways.
Jonah when on a hill and sulked. God saw Jonah and knew how he was feeling. God told him that he loved everyone and he doesn't like to destroy who are doing things bad. He would just like to see the people do good things again.