“SURELY I AM COMING SOON.” AMEN. COME, LORD JESUS!" – Every prophecy regarding Jesus' first coming was fulfilled literally, and every prophecy about His second coming will be fulfilled literally. Jesus' promise to return must have encouraged John when he endured exile on the island of Patmos. John sees additional images of New Jerusalem. The city's depiction stands in contrast to the ruin experienced during the tribulation, and evokes comparisons to the garden of Eden from the book of Genesis. After this, John relates several commands and messages from Jesus Christ. Among these are a dire warning not to manipulate the words of this message. Revelation, along with the canon of Scripture, ends with a benediction and prayer for Jesus to return. John and the other disciples heard Jesus promise: "I will come again and will take you to myself, that where I am you may be also." We cannot claim to know exactly when that moment will arrive. His coming may be soon — today or tomorrow, but the time of Jesus' return is locked up in the counsels of God. Whenever He comes, the event will occur quickly. First Corinthians 15:52 describes the event as occurring "in a moment, in the twinkling of an eye."

............................................................................................................................................................

“Surely I am coming soon.”

Amen. Come, Lord Jesus!"
BibleRef.com

What does Revelation 22:20 mean?

In this verse we read Jesus' affirmation that He is surely coming "soon."

As with similar statements in Revelation, this is translated from the Greek word tachys, which most literally means "quickly."

This is more a statement on the way Jesus will return than a claim about when He will return.

While there are no more major events left preceding His return, we cannot claim to know exactly when that moment will arrive (Matthew 24:36).

His coming may be soon — today or tomorrow, but the time of Jesus' return is locked up in the counsels of God.

Whenever He comes, the event will occur quickly.

First Corinthians 15:52 describes the event as occurring "in a moment, in the twinkling of an eye."

John and the other disciples heard Jesus promise: "I will come again and will take you to myself, that where I am you may be also" (John 14:3).

We also read the apostle John's prayer: "Amen. Come, Lord Jesus!"

Every prophecy regarding Jesus' first coming was fulfilled literally, and every prophecy about His second coming will be fulfilled literally.

Jesus' promise to return must have encouraged John when he endured exile on the island of Patmos.

John sees additional images of New Jerusalem.

The city's depiction stands in contrast to the ruin experienced during the tribulation, and evokes comparisons to the garden of Eden from the book of Genesis.

After this, John relates several commands and messages from Jesus Christ.

Among these are a dire warning not to manipulate the words of this message.

Revelation, along with the canon of Scripture, ends with a benediction and prayer for Jesus to return.

Revelation 22:20 Parallel Verses 

Revelation 22:20, NIV: "He who testifies to these things says, 'Yes, I am coming soon.' Amen. Come, Lord Jesus."

Revelation 22:20, ESV: "He who testifies to these things says, “Surely I am coming soon.” Amen. Come, Lord Jesus!"

Revelation 22:20, KJV: "He which testifieth these things saith, Surely I come quickly. Amen. Even so, come, Lord Jesus."Revelation 22:20, NASB: "He who testifies to these things says, 'Yes, I am coming quickly.' Amen. Come, Lord Jesus."
.
Revelation 22:20, NLT: "He who is the faithful witness to all these things says, 'Yes, I am coming soon!' Amen! Come, Lord Jesus!"

Revelation 22:20, CSB: "He who testifies about these things says, "Yes, I am coming soon." Amen! Come, Lord Jesus!"

BibleRef.com is an ongoing project aimed at creating a comprehensive, free, original, online commentary of the entire Bible. Many people avoid deeper Bible study because they are intimidated. They see the Bible itself as too big, too complex, or too obscure to understand. Many Bible commentaries are filled with slogans, religious jargon, and ten-dollar words. It’s difficult for the common person to find a commentary they can relate to.
In order to correct this, BibleRef.com is built around three core principles. These are Biblical Authority, Accessibility, and Discipleship. Each line of commentary, and every article, is weighed against these principles.

https://www.bibleref.com/Revelation/22/Revelation-22-20.html