How do we know that Jesus is real. Many writers wrote about Him, some of them knew him and spent considerable time with Him. There are over 9000 mentions of Him in the New Testament and thousands of word recorded that was spoken by Him. There are more witnesses for Him than any other person in ancient history.
Matthew and John we His disciples. They spent three to four years with Him; they heard him preach and teach. They witness miracles done by Him. They recorded many things that Jesus said and did. This was first hand accounts.
There are about 100 years between the time John wrote the Book of John and the earliest fragments of his gospel. P66 contains several pages of the book of John and has been dated to the second or third century. This alone give great credence to the authenticity of the Book of John.
The New Testament contains a book by James the brother of Jesus. Here we have the brother of Jesus writing a book supporting the movement started by his brother. Written around 60 AD, the earliest know copy is from the 4th century. See https://www.biblegateway.com/resources/encyclopedia-of-the-bible/Epistle-James for a discussion on the acceptance of this book/letter as being written by the Lord’s brother.
Jesus Christ is real. He existed here on earth. He was witness to by many. We have information on where He was born, His family, His ministry, many of His actual words, how he died and arose.
From faithfoundedonfact.com “There’s no better-documented series of books in all of ancient history than the books of the New Testament. So how many books are in the New Testament? The New Testament has 27 books written by 8 authors. We have over 25,000 ancient hand-written manuscripts confirming the New Testament. It is by far the most manuscripts of any book in the ancient world. The sheer quantity compares with just a few tens or hundreds of other ancient works. See https://faithfoundedonfact.com/how-many-books-new-testament/