"Behold, I am making all things new." Revelation 21:5
"In the original Greek" is a sad church cliche, and too many times it comes before a lot of really bad second-hand misinformation. Fortunately, I'm not offering anything except a couple dictionary definitions. In Greek, there are two distinct words, both translated as "new," but with radically different connotations. Neos means "new" as we normally think of it: a new car, a new book, a new day. Something that was recently created, that hadn't existed before.
But neos is not the word John uses here. What we have here is kainos, which also translates as new but in a very different way. We might better think of it as "renewed." Like, I'm going to fix up this old house so it's "good as new" - so it's kainos. The house isn't "new," but it has been restored and, in a sense, re-newed.
The Jesus of Revelation 21 is not a Jesus coming to blow this universe to smithereens and start over with a "new" one - although we often get that sense from certain Christian books and teachings.
No. The Jesus of Revelation 21 is "making all things new," that is, re-newing all things. In the same way that Christ bring's Israel's storyline to fulfillment, he is bringing the story of the universe to its ultimate goal and purpose. In the same way the resurrected Jesus both was and wasn't a "new" man (depending on which definition you use), the universe of Revelation 21 both will and won't be a "new" universe.
The Jesus of Revelation 21 isn't offering a divine reset button. He's promising that all the brokenness of this Creation will be reconnected with God's original vision for it, and that we will once again be "good as new."