But Jesus adds this statement - as such the word "but" has been inserted. It is basically an additional requirement to enter the spiritual realm.
What does it mean?
The key Greek words in the sentence are: εἰμί (whoever), πρῶτος (first in line or succession), and ἔσχατος (last). In other words, εἰμί is defined in the Greek lexicon as "to be, to exist, to happen, to be present" in the singular person. In other words, the use of the word "many" in this translation would be inappropriate. We are talking singular. In other words: each person - every person.
"Whoever is first shall be last, and whoever is last shall be first."
"Behold, I am coming soon! My reward is with me, and I will give to everyone according to what he has done." (Rev. 22:12)
He who testifies to these things says, "Yes, I am coming soon." Amen. Come, Lord Jesus. (Rev. 22:20)
This is why the Revelation text 22:17 discusses "The Spirit and the bride..."
“ ‘Love the Lord your God with all your heart and with all your soul and with all your mind.' This is the first and greatest commandment.” (Matt. 22:37-40)
(For a translation of Jesus' statements from the Book of Matthew without institutional sectarian influence, see the Gospels of Jesus - translated from the original Greek texts.)