It is my theory that Jesus survived the crucifixion and was put in a tomb. Then Allah took Jesus from the Tomb into Heaven..This is a theological-supernatural theory, it can't be disproven by Christians since they do believe in the supernatural.  After that the disciples had visions of Jesus (Several Scholars both atheists and Christian scholars--like Raymond Brown, James Dunn, etc say the disciples had visions after Jesus) and it was Paul who claimed that Jesus was crucfieid and resurrected and his "gospel" beat out the disciples "gospel" (whatever their gospel might be). This explains the Quran 4:157. From the New Testament we see evidence that the disciples were not preaching the same doctrine and they did not believe in the same Jesus. See here. Also it's very possible that Paul believed Jesus was resurrected given a new spiritual body, Paul believed in a "spiritual" or "visionary" resurrection of Jesus. For more on the very possiblity of the spiritual resurrection of Jesus see here.  Refuting the claim that 1 Corinthians 15:3-8 says that the disciples believed in the death and resurrection of Jesus see here. We don't know what stories Paul got from the disciples of Jesus. When Paul is arguing for the resurrection he never cites this information, when he says "what I hand to you, was handed onto me" he uses the exact same phase in Galatians 1-- he received it in a vision from Jesus--- he received the revelation not from a man-- and this was 3 years before he talked to the disciples. 

The reason why Christians and Atheists say Jesus died is because Christians believe Jesus died--- for theological reasons, because of their belief in the New Testament, etc. The reason why Atheist and Atheist scholars say that Jesus died on the cross is because they don't believe in the supernatural, they don't believe that God could have kept Jesus alive thru the crucifixion process. So they won't allow the belief that Jesus survived the crucifixion, because it's a supernatural belief and the atheists don't believe in the supernatural. 

Some Muslims might argue that Jesus was not crucified rather someone was crucified instead of Jesus. However the Quran NEVER says this in the original Arabic text and Prophet Muhammad (peace be upon him) NEVER said that someone else was put on the cross instead of Jesus. These theories that someone else was put on the cross instead of Jesus were just opinions that Muslim commentators said, but these are not biding on us. In Islam the highest authority is the Quran and Prophet Muhammad (p) and the Prophet NEVER said someone else was put on the cross instead of Jesus. Even Shabir Ally (WHO IS A SUNNI MUSLIM) Says this.  

 

WHAT ABOUT JESUS IN THE NEW TESTAMENT PREDICTING HIS DEATH AND RESURRECTION? 

This was already been dealt with here. 

This has already been dealt with here. For atonement in Judaism and how Atonement in Judaism contradicts antonement in Christianity see here and here. Also in Judaism there were three ways to get atonement from sins: 

                  -Animal Sacrifices 

                  - Consistent repentance and prayer 

                  - Charitiable Deeds (See Daniel 4:2-8) 

I also suggest reading this book which shows that Jesus assumption into heaven was an earlier belief rather than the resurrection. Also see here. Also see here. So do we have very good evidence that there was a very early belief amongst Christians that Jesus was taken into heaven hence his assumption, rather than his resurrection. There was even Jewish beliefs of assumptions or disappearances of indivduals into heaven. See here. In all the Gospel accounts nobody sees Jesus rise from the dead. They only observe a missing body and are later visited. However these visitations sound very visionary (For example see Mark 16:12, Luke 24:16, John 20:14, etc) 

Also want to state that there is NO evidence that the disciples believed and preached that Jesus was crucified and ressurected-- the Christian apologists would have to prove that, there is no way they could. Paul got into fights and had disagreements with the disciples, the disciples and Paul were NOT preaching the same things about Jesus. See here. For the unrealibility of the New Testament documents see here and here. Also see Bart Ehrman's book Forged to see evidence that most of the New Testament documents are forged. So how can we trust people we don't even know? As for the disciples of Jesus journeys and martydoms, these are mainly based on myths and legends. For more on the disciples see here. I also suggest reading this book which talks about the historicity of Jesus disciples.  For unrealibility of Acts of the Apostles see here. So the New Testament documents aren't reliable.Even conservative scholars will admit that we don't know who wrote the Gospels or who their sources are. Yes the New Testament documents may be early, but just because something is early that doesn't mean it's reliable. The New Testament documents misquote the Old Testament passages, we don't know how wrote a majority of them, and we don't know their sources. So how can we trust the New Testament documents? We can't.