You must prophesy again about many peoples, nations, languages and kings

 Revelation 10:1-

“There will be no more delay! 7 But in the days when the seventh angel is about to sound his trumpet, the mystery of God will be accomplished, just as he announced to his servants the prophets.

Then the voice that I had heard from heaven spoke to me once more: “Go, take the scroll that lies open in the hand of the angel who is standing on the sea and on the land.”

He said to me, “Take it and eat it. It will turn your stomach sour, but ‘in your mouth it will be as sweet as honey. I took the little scroll from the angel’s hand and ate it. It tasted as sweet as honey in my mouth, but when I had eaten it, my stomach turned sour. Then I was told, “You must prophesy again about many peoples, nations, languages, and kings.

Why?
No one knows what will happen in the future, but the Lord let John see the future visions. And the Lord allowed part of the vision to be written down as a reminder to us.

The word of the Lord, described by John is prophesies many peoples, nations, languages, and kings. It does not happen as mentioned by men or kings.

How?

We don't need to know what or when the time of the Lord, but let faith, love, and hope stay in my heart and mind.