In dealing with your friend, I would show him John 1:1, which says, “In the beginning was the Word, and the Word was with God, and the Word was God.” Then I would show him John 1:14, which says that “the Word became flesh and made his dwelling among us. We have seen his glory, the glory as of the only begotten of the Father, full of grace and truth.” This verse clearly tells us that Jesus is the Word and John 1:1 affirms that the Word was God.
I would also show him John 20:28, where Thomas, the skeptic, speaks directly to Jesus and says to him, “My Lord and my God.” And we see from the following verse (29) that Jesus fully accepted that ascription of deity. If Jesus was not God, for him to have accepted that ascription of deity would have been blasphemous. However, it is clear that he accepted it.
There are many other passages that support the deity of Christ, but these are easy to use. I hope they prove helpful in dealing with your friend.