Why is the bible the word of God?

I was talking to a guy on a post here recently and we were debating about whether or not homosexuality is a sin. I pointed out Romans 1:26-27 and he basically said that that's something that the jews believed in and that God doesn't necessarily agree with that.

Now, I thought that was crazy. Like, it's written on the bible, which is literally the word of God, WHAT DO YOU MEAN he doesn't necessarily agree??

But then he raised some very interesting points and now I'm confused. WHY is it the word of God? Why is it not just INSPIRED? Why do we take it as THE ultimate truth and not just different views about God stitched together?

I know it's His word but I have 0 coherent arguments to prove why. Can y'all help me out?