The way I see it , as a muslim, is that Qur'an confirms the existence and stories of certain individuals who are talked about in the Bible. Not to mention, often the details differ, thus correcting on the narrative. Qur'an confirms their truthfulness as warners/messengers/prophets authorized by God. This is not to say that the modern Bible that we see is filled with all true stories dictated by God.
Lets put it this way, you know prophet zoolander ?? Dont worry, me neither !! But when a jew/christian comes up and speaks about David, Moses, Jesus.... we instantly recognize them, even those among us that has never opened the OT/NT or met a christian or a Jew.
Now which part of the modern Bible is made up, and which is true, although interesting, its irrelevant for me. My contract with God is exclusively based on Qur'an. If you are/were a christian , it is your duty to verify your book, ask questions, study and walk your own path.
---------- Student of Allah