How can we know if the halacha we have is accurate and in accordance with the original will of the Holy One, blessed be He?

Indeed, there is no way to know. But it says two things: 1. Even God is supposed to know that there is a tradition and that it can go wrong. 2. We do not have a more accurate version than the one that is the result of our best efforts. Beyond that, God Himself writes in the Torah, “If anything should surprise you… then arise and go up to the place,” meaning that if there is doubt about the halakhic law, we must go to the Sanhedrin and hear its voice. In short, when we say that the halakhic law in our hands is correct, we mean that this is what should be done normatively, and not that this is authentically what was delivered to Moses at Sinai. You could ask who told us that the judge’s interpretation of the law is accurate? Why listen to him? Here too, it’s the same answer.