Can you ask your friend to be more specific in his claims? I am not asking to put him or you on the spot but this could be addressed from several different avenues. Here is a very short statement from an expert in the field of Judaism that would disagree with your friend:
The main point is that Judaism and Christianity agree on the sanctity of the Old Testament = Tanakh, but disagree about its meaning.
Neusner, J. (2006). Between Time and Eternity: The Essentials of Judaism (p. 8). Eugene, OR: Wipf & Stock Publishers.
He goes on to say that most Christians don’t take into account the oral Torah, Mishna, which is inseparable from any understanding of Judaism as we know it from the 1st century to the present. Here is what Neusner had to say.
We have already observed that Tanakh (“Old Testament”) supplies the prehistory of Christianity. It also provides the foundations of Judaism—specifically, of the form of Judaism that dominated from the late first century to modern times and continues to flourish in the present age. That Judaism is called rabbinic, because its teachers are rabbis; or talmudic, because its teachings are contained in and authoritatively taught by the Talmud (which we shall describe shortly); or normative, in the sense that all other modes are declared heterodox or heretical—a highly theological adjective; or classical, in the sense that this mode of Judaism is deemed authoritative and of enduring excellence—another theological adjective. In alleging that Rabbinic Judaism begins in the first century, of course, we ignore what Rabbinic Judaism says about itself: that it was revealed as part of the Law when Moses received the Law from God on Mount Sinai…When God revealed the Torah to Moses at Mount Sinai—that is, the events depicted in the Book of Exodus—revelation took two forms. One is the Written Torah, which is widely known. That consisted to begin with of the Five Books of Moses. Under the inspiration of God, various other prophets, psalmists, and chroniclers added to the sacred Scriptures.
Neusner, J. (2006). Between Time and Eternity: The Essentials of Judaism (pp. 10–11). Eugene, OR: Wipf & Stock Publishers.
Maybe this will help you move the conversation along as you continue to learn. God bless you in this endeavor,