Why did Adam and Eve die?

There lived a happy couple, Adam and Eve, under the love and protection of God in the Garden of Eden. One day, the cunning serpent approached them. The serpent deceived Eve to eat the fruit from the tree of the knowledge of good and evil forbidden by God. She also gave some to her husband and he ate it. As a result, they were expelled from the happy Garden of Eden due to the sin of disobedience and lived painful lives.

And they died in the end according to the words of God.
Even non-Christians will know the story of the Garden of Eden. The Bible says that death came to all people on this earth due to disobedience of Adam and Eve (Romans 5:12.)
Are there any ways to recover life? Numerous Christian churches emphasize faith, shouting “We can be saved as long as we have faith in God! Do you believe?” Of course, we can have the promise of salvation through faith. Then, didn’t Adam and Eve believe in God when they ate from the tree of the knowledge of good and evil? Yes, they did. Adam and Eve and even their descendents had faith in God.

 If such insistence that “we can be saved as long as we have faith” is correct, Adam and Eve should have not died and live happily in the Garden of Eden until now. This shows that faith alone does not necessarily lead to salvation.
Adam and Eve believed in God. What didn’t they believe?
They did not fully believe in the words of God: “You must not eat from the tree of the knowledge of good and evil, for when you eat of it you will surely die.” They suspected the words of God with their own thoughts such as “Well, that’s not gonna happen. How can I die if I eat from it? It’s good for food and pleasing to my eyes.”
God wants us to have such faith that we can believe in the words of God absolutely, even the part which may not be possible to believe with the human thoughts.  God judges our faith through the “Passover of the new covenant.”
Jesus said to them, "I tell you the truth, unless you eat the flesh of the Son of Man and drink his blood, you have no life in you. Whoever eats my flesh and drinks my blood has eternal life, and I will raise him up at the last day. (John 6:53-54)
So the disciples did as Jesus had directed them and prepared the Passover… While they were eating, Jesus took bread, gave thanks and broke it, and gave it to his disciples, saying, "Take and eat; this is my body." Then he took the cup, gave thanks and offered it to them, saying, "Drink from it, all of you. This is my blood of the covenant, which is poured out for many for the forgiveness of sins. (Matthew 26:19-28)
God promised that “those who keep the Passover have eternal life.” What will you do? Are you going to reject observing the Passover with the thought “How can we have eternal life with such Passover bread and wine?”
Adam and Eve were kicked out of Eden although they believed in God to the end. Empty shouting such as “I believe in Jesus only” is not faith! It’s no more than autohypnosis. True faith is to believe in and follow the words of God—even something that is hard to believe with the thoughts of men.