Do not worry, the end of the world will never come because of unattainability the end of infinity.
Eternity is determined by the fact that the moments extracted from it never end.
Will people be able to populate the entire universe?
They have already settled it, but don't know about it.
The world exists only in order not to put up with it.
Will the light final?
Not now, but next time. There is enough light for now.
Why is the universe expanding?
Unlike us, it has somewhere to go.