I can’t imagine why anyone would tell you that Jesus is dumb. She may not believe that Jesus was the messiah, but nearly the whole world agrees that Jesus taught lovely things, and reveres Him as a teacher. I am Jewish, but I would certainly never denigrate Jesus. The Sermon on the Mount is one of the most beautiful passages in all the world’s literature.
Jews are the people from whom Jesus sprang. They mold their beliefs essentially on the first part of the Bible which you call the Old Testament. Christianity and Judaism are so tied together that we call ourselves Judeo-Christians here in the West.
Jews may believe that Jesus was an important historical figure, but they stop short of believing that He was the Son of God, and that has always made tensions between Christians and Jews, but the foundation of Christianity is Jewish, and you will probably be surprised to find out how much you already know about being Jewish without realizing it.
There is a wonderful book called The History of the Jews by a non-Jewish man named Paul Johnson, in case you are interested in learning more.