From a Christian perspective or Jewish perspective the Koran picks pieces of Scriptures, using some, elaborating on some, perverting some. But most of the material in the Koran has no relationship to the Hebrew or Christian Scriptures as they are understood by most Jews or Christians. The Koran has its own mission to supplant and replace all religious texts and legal codes.
Well, you're wrong.
The Muslims claim the Koran's origin is divine.
Not sure which Muslims you're talking about, but Muslims I've talked to believe Jesus to be Divine and that Koran to be the text from which they themselves follow.