The people who wrote the scriptures that make up the Bible experienced God and Jesus Christ for themselves and that is what they wrote about. They testified about God, about Jesus Christ because they KNEW Him for real.
The people who wrote the gospels (Matthew, Mark, Luke & John) recorded what Jesus said, what they saw, what they heard. They touched Him. The apostles who wrote the letters of the New Testament also knew Jesus for real. They received the Holy Spirit and they were guided by the Holy Spirit, they KNEW Jesus, they knew that He IS alive, they testified that He is ALIVE. They followed Him, they didn't follow books or other people. They testified of God, of Jesus Christ.
Have you come to know Jesus Christ FOR REAL since you read the Bible? Or do you still just read the Bible? Do you listen to people and follow them? Do you take the word of people or have you come to know Jesus Christ HIMSELF for yourself? Do you know Him for real? Do you hear from HIM or from people? Who do you follow? If you know Jesus you will follow Him and you will have a testimony, you will witness that Jesus is alive.
If you do not know Him for real, you do not hear His voice, you do not experience Him then you DO TO KNOW HIM! HE will say to many believers who just read the Bible and listened to other people, Jesus will say to them:”Go away I never knew you, you workers of wickedness.” Do you KNOW Jesus Christ? Do you hear from HIM? Those who are led by the Spirit of God THEY ARE THE CHILDREN OF GOD. Are you led by the Spirit of God or to you accept the testimony of other people, do you run after other people? Because then you will fall into the ditch. You need to KNOW Jesus, LISTEN to His VOICE and FOLLOW Him.
Seek Him UNTIL YOU FIND HIM! Jesus Christ is ALIVE. You must hear from Him FOR YOURSELF.
May Jesus bless you.