When do you think the whole world would be a better place?

when people learn to be decent human beings

The world will become a better place when all living beings choose to acknowledge the fact that we are not perfect. We need to fix what we have done. We need to not be headstrong and own up for what we have done. Then the world would be able to become a better place because we would be able to finally improve.

Explanation:

No. If a clause is followed by a list, it should be preceded with a colon instead.