Allah recognizes that the Bible is perfect -363

To justify the existence of Koran and by this that of islam, the moslems want believe than the Koran would be the eternal God word (Koran 43.2-5), that was sent for confirming and replace the book that was there earlier, this means the Bible (Koran 5.48). So, if the Koran is eternal, but how could itself to confirm or replace it that has been earlier it. But why, what is the reason to confirm it that we want replace ? But mainly, Allah himself recognizes that there is not of doubt at subject to the Bible. (Koran 10.37) From then, but why to confirm her or replace her ?