QUESTION : Why do Christians try to convert Jews, can't they leave us alone?
This is your question, Miriam. I think what you really mean is that why do Christians preach to Jews, why don't they preach to their own people?
The simple answer, that you won't be happy with, is that Jews, along with everyone else, need to hear the Christian message. In fact some would say that Jews especially need to hear this message. There are three reasons why many Christians consider it important for Jews to do so.
The first, the general answer, is that we Christians consider it our mission to 'share the good news' with everyone, Jew and Gentile. Jesus called it the 'Great Commission', saying "All authority in heaven and on earth has been given to me. Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, and teaching them to obey everything I have commanded you. And surely I am with you always, to the very end of the age."
The second reason is that many Christians feel indebted to Jews on account of the Jewish background of Christianity. The New Testament writer, Paul, puts this into words, "Theirs is the adoption as sons; theirs the divine glory, the covenants, the receiving of the law, the temple worship and the promises. Theirs are the patriarchs, and from them is traced the human ancestry of Christ, who is God over all, forever praised! Amen."
Of course there is an element of guilt on account of the terrible treatment of Jews at the hands of so-called Christians in the past, but that is unavoidable and Christians want to look to the future, not the past.
Finally, there are some Christians who feel a specific calling to Jewish people, who they sincerely love. These people would be found in Messianic Fellowships, congregations where Jews and Gentiles worship together in a Jewish context and with a desire to explore the Jewish roots of their Christian faith. These people would actually consider it anti-Semitic not to pray for and feel burdened for the Jewish people.