Okay. So you want to know why the New Testament has nothing to do with Jesus or his disciples?
1. Tell me which book calls itself by the name of the disciple of Jesus and authentically confirmed to be. I can prove that the answer is "none".
2. No one who ever wrote anything in the Bible has ever met Jesus. They dont even claim to have.
3. When you say the New Testament why dont you accept the epistle of Barnabas, the Shepard of Hermas, Epistles of Clement as part of the New Testament? They were in the early canons. So please explain. Which disciple wrote them? Was clement a disciple? Was Barnabas a disciple?
4. Every single book in the NT was written several decades after Jesus passed away. This is not based on manuscript evidence because manuscripts begin only in the 2nd century and we have only one dating to the early second century called P52, which a small manuscript of several inches. Thus, this dating that I am speaking of is based on the text of the book which dates them several decades after Jesus. e.g. John, the corner stone of NT theology, was written 70 - 80 years after Jesus.
Now you are using the Quran to affirm the NT. But the Quran does not speak anything about the NT. Quran speaks of the Gospel that Jesus was preaching. It just mentions the Gospel that Jesus preached. That is not the book called the NT. You are using a very common Christian evangelic apologetic which is good for shouting at people at speakers corner sis, but its not valid. Walk beyond this type of daily repeated false apologetics of others.
When the writer of Matthew says "peached the good news" he is not referring to his own book. He is not referring to his own book as "Gospel". He is referring to what Jesus preached. Jesus was preaching euaggelion tis basilias. The Good News of the Kingdom. The writer never intended to call his own book "the Good News of the Kingdom". He is referring to what Jesus preached which is cloven from what he is writing.
One could begin there.
That does not prove the Quran is from God, and Bible is not from God.
If an Atheist who does not believe in God, or that Jesus was a Messenger of God, says, I don't believe Bible is inspired by God, his beliefs are consistent.
But if someone, a Muslim says, I believe in God, and that Jesus was a Messenger of God, and the Messiah, but I dont believe Bible is legitimate and trustworthy, this belief is not consistent.
Remember, in Islamic theology the Book that a Messenger leaves for His followers is very important. The most important thing.
Both Sunni and Shia agree.
Here is a Hadith from Prophet:
"I have left with you two things which, if you follow them, you will never go astray: the Book of God and the
sunna of His Prophet"
Shias, also agree with this Hadith, as regards to the Quran. For them Sunna, is also traditions of the Imams.
But, both Shia, and Sunni agree that, after the Messenger left, He left the Quran as an important thing, to guide them.
Now, with regards to Jesus, when He left, the mainstream Muslim, says, Jesus did not leave any legitimate Book.
From Jesus, until revelation of Quran, there are 600 years. According to such a belief, for 600 years, those people were left without a legitimate book. Was God incapable to leave a proper book for them?
This is the inconsistency in Islamic belief.
Moreover, just as you say, God created the world and human, through evolution (not by literally creating Adam from dust, with His own hand), you shouldn't have problem believing God made the Bible appear, and written legitimately, even if it was not written by the hand of Jesus or apostles.
I have raised this inconsistency, and debated with many Muslims about this belief, but never got any reply. Instead they try not to answer directly these problems. I hope you are able to see.
Good luck