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?

Hello, Honorable Rabbi, a secular friend who works with me asked me a question that I didn’t know how to answer. He said that even if the tradition of the Torah is reliable, how can we know that the halacha and the conclusions of the tradition are the conclusions that are desired in the eyes of the Holy One, blessed be He, and that they are relevant to what really needs to be done? I would also appreciate reading materials if that’s okay.