Judaism Is Misunderstood By Many Christians.

A lot of Christians misunderstand Judaism. Firstly, some Christians see the religions as brother faiths, both seeking after the same God, but just from different perspectives. But Jesus said if you deny him you reject the father. In this way they have vary divergent beliefs and traditions. Jews tend to view Christians as Esau, the rejected brother of Jacob, never to be reconciled. 

As this book review from the Jewish magazine Haaretz notes, significant Jewish religious leaders, such as Yeshayahu Leibowitz are incredibly disdainful of Christianity; 

"Leibowitz used abusive language against Christianity, refrained from calling Paul the Evangelist by name and termed him an apostate “by spite,” in contrast to the narrative of his conversion from deep conviction and after Jesus was revealed to him. Christianity is an “abomination of desolation,” paganism that maliciously falsified symbols borrowed from Judaism. “We curse Christianity three times every day,” Leibowitz wrote...

Christians are dangerous heretics according to Orthodox Jewish theology. 

Secondly, Christians often mistakenly believe Judaism is a religion of the Old Testament and that it is the same religion as the faith of Moses. But this is untrue, as the same article notes:

"...A final comment refers to the nature of the “Judaism” with which the Church seeks reconciliation. A reader of Ben Johanan’s book comes away with the impression that almost all the steps taken by Christian theologians refer to Judaism as the religion of the “Old Testament,” which preceded Christianity. This suggests that the dialogue between the two religions is only in its infancy, because Judaism is not the religion of the Bible but the religion of the Talmud, the rabbinical literature, the kabbala and prayer. Christian theology is still conducting a dialogue with itself – not yet with the Judaism that existed parallel to it."

Judaism is not an Old Testament tradition. It is a religion based on the traditions of the elders that Jesus condemned and noted had departed far from the words of God (Mark 7:1-13). Modern Rabbinical Judaism is not a biblical faith, it is the descendant of the faith of the Pharisees which Jesus was very clear was a Satanic departure from the true Jewish faith (John 8:39-59). Jesus told the first century Jewish leaders that if they really believed in God they would believe in him, because he was from God. As the disciples and Paul the ex-Pharisee later believed. You cannot reject Jesus and believe in God. This is basic Christianity (John 14:1-11). 

It's still incredible to me how many Christians are not aware of this. But then again, is this really taught on often? Christians, too often, see Orthodox Jews as co-believers in God. But Jesus is the representation of God, the fullness of his image (Col. 1:15). To reject Jesus is to believe the lies of the devil and to reject God absolutely. It is to believe in a whole other religion. 

I recommend reading the whole article, because it will make the differences between the faiths very clear. Christianity and Judaism are not brother religions, anymore than Christianity and Islam are. If you want to understand how to reach the Jewish people you need to understand this, just as this article explains: Christians make seriously wrong assumptions about the relationship of these two faiths. In treating Judaism as an Old Testament faith, it is actually only talking with itself.