One way to deal with him might be to hand him a Bible and ask him to show you one of these alleged errors or contradictions—because in my experience, most people who say things like this have never actually read the Bible.
But remember: You aren’t trying to win an argument with him, nor are you trying to embarrass him. Your goal is to point him to Jesus, and everything else is secondary. He may well have questions about the Bible that need answering before he’ll begin to think seriously about its message—and if so, you should offer to help him find those answers. Your pastor or local Christian bookstore may be able to help you do this.
On the other hand, many people who claim they have questions about the Bible actually have a far deeper problem: They don’t want to turn their lives over to God. You could answer every question they asked and they still wouldn’t believe—because that’s not their real problem. Their problem isn’t with their mind but with their will, and they need to face it.
Do you remember “doubting Thomas,” Jesus’ disciple who refused to believe He had been raised from the dead? Jesus’ response to him was simple: “Look at my hands and my feet. It is I myself!” (Luke 24:39). And this is what you should encourage your friend to do—to look at Jesus as He is presented in the Bible. No one who honestly examines Him will ever be the same.