If you are Jewish then you have to be a jew?

Answer 1

1) Judaism isn't like being a citizen of a country, which one could renounce. If you're Jewish, you're Jewish. So the answer is yes.

2) However, we do have free choice (Deuteronomky 30:15-20). One can choose not to live as a Jew. In that case, the "flame" of one's religion flickers and diminishes....but it never dies out. One can always return (do teshuva). Very many Jews today were born into non-religious families and chose to return to the Torah of the Jewish people.

3) If a Jew becomes a believer in Christianity ("Jews for Jesus;" messianic Jews), the consensus in the Jewish community is that he/she has ceased being Jewish. The same applies to Buddhism and other non-Jewish beliefs. Nonetheless, even such a person can do teshuva (return to Judaism).

Let me tell you a true story, which took place some four decades ago. A good friend of mine (this was before we had met), who was born Jewish but knew nothing of his religion, decided to live as a Buddhist. He began practicing it fully, learning it, etc. Eventually he traveled to the Far East, where he invested a great deal of effort in seeking out a venerated Guru, who lived on a remote mountaintop. When he at long last reached the goal of his journey and told the guru a little about himself, the guru said to him: "but have you explored your own religion?"

This fellow is today a well-known rabbi here in Israel.