The Torah was written by G-d. The books of the Nevi'im were written under the Spirit of Prophecy (Nevi'ah), which is a step lower. The books of the Ketuvim (writings) were written under Ruach HaQodesh ("the holy spirit" or "Divine inspiration") which is a step lower still. The 'Anshei HaKenesset HaGedolah (Men of the Great Assembly) canonized the Prophets and Writings and closed the canon. No one has ever had the authority to add another book.
The "new testament" you are so fond of was added by the Catholic/Orthodox church, which you probably don't agree with. If you recognize their authority to add to the Bible, you might as well accept their other religious beliefs as well, hadn't you?
We believe this because we are indwelled by the Holy Spirit,
Which means what? You believe it because you have a funny feeling? You believe it because that's what you've always believed? You believe it because that's what you've always been taught? One doesn't need a "funny feeling" to know the Torah is from Heaven. And the Torah does not provide for any such religion as chr*stianity.
and believe Y'shua to be the Messiah, who is the ultimate sacrifice for all sin, for Jews and Gentiles alike. A relationship with Y'shua doesn't make any of us superior to anyone else; but simply forgiven, by God's grace alone.
You believe this because you don't know what the Messiah is or what he is supposed to do and because you accept a priori the right of the "new testament" to "authoritatively" interpret the Hebrew Bible (in other words, you believe it because you already believe it, which is the same reason evolutionists believe in evolution). And by the way, no one believed Jesus' death was an atonement for sin until the Middle Ages when St. Anselm invented that theory. Ask any Catholic or Orthodox FReeper.
That being said, most of us realize that we and religious Jews both worship the God of Israel, and we love our Jewish brothers and sisters as ourselves, as God commands. Shalom.
I am not Jewish. If I were I'd probably just smile at you. I'm a Noachide who used to believe exactly as you do and who is driven to distraction by people who reason in circles.
Shalom to you nevertheless. May G-d lead you ever further into truth.