Torah from heaven

My question is how can I know that at least the basis of the Torah that we have was indeed given by God, even if we assume that if the people in the Land of Israel did not hear from their ancestors that they were slaves in Egypt and that they came out in a supernatural way, that this appearance made them think that Moses was God's messenger, and in addition, they heard from their ancestors that they met God in the desert and that he gave them the name Torah, and if their ancestors did not tell them all this, it is hard to believe that anyone would have been able to sell it to them. But if this is what they heard from their ancestors, then the other small details, such as what miracles exactly there were, etc., make sense that they did not remember exactly. And if suddenly they supposedly found the book that Moses wrote, then it is possible to sell that this is indeed what happened, and the question is whether the fact that a group of slaves was convinced by miracles and revelation proves that it did happen (by the way, in Judaism it is said that only a fifth of the people came out, and perhaps it was only the group that was convinced by Moses' supernatural power and therefore went with him). The part of the revelation, in my opinion, is the most unproven, since what was there was fire and trumpets. And Kol, although a rhetorician, can convince them that it is God, but in reality, you don't even need magic for that, and also the part of the many miracles such as the ten plagues, the only proof is that they came out in miracles, but there is no proof that these are indeed the ten exact plagues, and the Torah describes that something like turning the entire river into blood or maybe even all the water in Egypt into blood is written about that the magicians did that too, and the Torah describes that something like filling all of Egypt with frogs was also possible for the magicians, so is it outrageous that someone who grew up in Pharaoh's house and was also sent to the best school for magic surpassed his masters and performed slightly greater magic and caused a group of slaves who worked 24/7 and were not given time to become wise and wise to believe that it was more than just magic (and I want to mention that the Sages describe Pharaoh as considering himself a god and therefore did not want to be seen doing his business, and was truly blind because of how many magicians the Egyptians believed he was To).