Wasn't it due to man's sin that God sentenced man to die?
God did not "sentenced" man to die.
God is holy. Sin cannot come before his presence. When Adam & Eve sinned, God cannot sustain their immortality since they have put themselves beyond God's perview/guardianship. God did warn them of the consequences of eating the forbidden fruit but they chose to disobey.
I have wrestled with the thoughts about why then that monkey's die, fish die, birds die, grass dies, etc.
Would all the above die if Adam & Eve did not eat of the forbidden fruit? Probably not because the bible states that through one man sin and death came into this world.
And I am confused as to the real truth as to why man dies.
No one knows "the real truth" as to why man dies. We are all searching. This is the best i have for now. Truly, man does not have to die. Interesting questions abound. Why can't every cell of our body replicate itself? Why can salamanders regrow their limbs, or a lizard its tail, or a sponge itself? Every cell in our bodies have telomers in their DNA. They keep track of how many times a cell replicate. Every time a cell replicate, its telomers get shorter. When it gets too short, the cell self-destructs - apoptasise. Cancer cells on the other hand, are our very own cells which have their "Stop Replicating" button switched off. Their telomers are also switched off. Cancer cells are immortal. As long as they have food, they keep on replicating. Why can't our normal cells also be like that - except with their replication under control?
That is what the science of Jerriatics (i'm sure i've got the spelling wrong) is all about. Adam & Eve were perfect; so maybe every cell of theirs can replicate forever. So i believe (on faith) that man does not have to die.
I can't imagine some huge tree falling on Adam's head, and the tree just snaps in half on his head, while Adam continues walking on his merry way?
Under God's governance as they were, God would have prevented this, or any other mishaps somehow, i think. But God would not have prevented Adam & Eve from eating the forbidden fruit as they were given the freedom of choice.
I have many questions regarding the truth of the Bible, and am not sure whether to lay them all out right here, and be done with them, or to start new threads for each one?
Nah, lay it on here, bro!