You are so right. The first huge problem with the credibility of Islam is that they recognize Jesus Christ as a prophet. Since Jesus Christ said He was God, he cannot be a prophet. He can either be who He says He is (God), or he can be a blasphemer, or crazy person. The fact that the Koran is so wrong about Jesus shows you cannot trust anything else in it.
and they believe he was not crucified. The hole notion that Islam is an abrhamic religion (judaisims and chrisitanity) is absurd in my opinion.
The way the Koran gets around this is by saying that the Gospels are altered from the actual word of God, and that only in the Koran is the true account revealed, directly from God to Mohammod.
Therefore any inconsistency between the Koran and the Gospels is due to the false writings of those who wrote down the Gospels. IOW, what Jesus said is only accurately rendered in the Koran, and therefore the Koran is consistent with Jesus, by definition