Adam lived to be 930 years old. What died the day he ate from the tree of knowledge of good and evil? We know it wasn’t his body because if it had, we wouldn’t be here. His soul didn’t go immediately to Sheol, so it wasn’t his soul. Adam breathing, eating, and procreating after he ate the forbidden fruit is evidence that death is not a cessation of existence; it is a change of state. The Adam on the other side of sin was not the same as the Adam before. His spirit was dead. As his children, we were born spiritually dead.
The Son declared on His exit from heaven that He knew the Father had no pleasure in the animal burnt offerings and sin sacrifices. Because His heart is to always bring pleasure to the Father, He did something about it. “Lo, I come to do thy will, O God,” He said. He came to save us, but His motivation was to bring pleasure to His Father.