This reminded me the nature of "lie" told by Satan.
God says to Adam: if you eat the fruit, you will "die".
Satan said to A&E: if you eat the fruit, you may not "die".
So, they ate the fruit. Did they "die"?
Both God and satan said the truth. But this one word "die" has two meanings. I would say that what satan said referred to the decease of animals, which Adam can easily understand. If so, satan was certainly telling them the truth. They ate the fruit, and they did not die, like an animal.
But I don't think Adam and Eve really understand what does God says to them. They do not understand the meaning of death told by God. Since there were created, God is always around with them. They never know a situation, in which they will never see God again.