Who said the one who is revealed is telling the truth?

peace,
Let's assume that we were present at Mount Sinai, or at least were born a few generations after it happened. So we had no doubt that it happened and there was a revelation there, etc.
The question still remains: How are we supposed to know that the One who reveals Himself to us, who gives us the Torah, and commands us with the commandments, is speaking the truth?
Maybe he is not the creator of the world, but a lesser being who still has the power to part the Red Sea, etc.
Unlike humans, who have the tools to examine or evaluate their words, or try to look for any interests they might have in lying, when it comes to a spiritual revelation that is not from this world, since we have no indication of whether he is speaking the truth or a lie, or the ability to compare to other revelations in which we know that they spoke the truth or a lie and to statistically evaluate, what is better than assuming that he is speaking the truth over assuming that he is speaking a lie?
And even if we say that revelation is something that cannot be described at all to a person who has not experienced it, like explaining to a blind person what it is to see. Even a person who sees can see illusions, in addition to the fact that it is not certain that as part of the tradition of the class there is also a clear tradition for this additional "sense".
Even a person who believes in the God who created the world, how can he be sure that this is indeed the one who is revealed to him?
 
thanks.