I know the Old Testament was written by the disciples (inspired by God),
For the most part we don't know who wrote the various books of the OT. Very few say who wrote them, and traditional authorship was never meant to be "Moses wrote all of these 5", but "These 5 carry Moses' authority". What we do know is that they were written, redacted, collected, collated, and chosen as useful by the people of God over many centuries.
but I was asked who wrote the
New Testament, and I thought they were written by the disciples too, but I was told wrong. It made me wonder, who created the New Testament, or was it already created like some say?
Again, what we know with certainty is that these are the books that the early church determined were reliable (they knew the provienence) and useful in church.
We know the authorship of a few with some certainty, we have an idea about others but there is dispute, and others we simply have no idea:
Matthew - traditionally the apostle Matthew but we have very little to back that up.
Mark - traditionally Peter's story as told to the Christians in Rome and written down by Mark. There is no particular reason to think that false, though we can't be sure who Mark is in other terms.
Luke - Traditionally Luke as mentioned by Paul. Certainly well researched.
John - Either the apostle John, or more likely the early community he founded recording his stories with his involvement.
Acts - The same author as Luke.
Romans - Paul
1 & 2 Corinthians - Paul, but may be some editting
Galatians, Ephesians, Philippians, Colossians - Paul, although his authorship of some is disputed by some
1 & 2 Thessalonians - Paul
1 & 2 Timothy and Titus - maybe Paul, maybe someone later writting under his authority
Philemon - Paul
Hebrews - we have no idea
James - James the brother of Jesus, leader of the very early church
1 & 2 Peter - Possibly the apostle Peter or possibly someone later writing under his authority.
1, 2 & 3 John - Probably the apostle John or his community writting under his authority.
Jude - Jude the brother of Jesus and James
Revelations - traditionally the apostle John but disputed by some. Revelations was the most contraversial book to make it into the canon.
Most of these books were decided to be 'canonical' with very little dispute - the early church had a very high degree of consensus that the books were reliable and useful. Only Peter and Revelations were particularly contraversial.