Problem dealing with death as an atheist

[Zenith]

The idea with the secret of life is not is not that people would disagree that a cell is formed of lifeless particles - no one disagrees with that (I guess). The idea is the thing that makes a cell function (i.e. live): is it only chemistry? is it physics laws? And what does it make the living cell cease to function? Can one revive a cell after it's dead for a day? if not, why (if the cell has every component there, what's wrong?)? How does a cell know what molecules to consume? Have you studied how the cell functions and can provide physical & chemical explanations that clarify absolutely everything?

Look up "Enzymes". That would be a great start to help you understand how these functions happen. Also look up "Virus".

That's not a good explanation. My question is "how exactly"?

I've taken a look about the enzymes, a thing that I did not understand

Some of the enzymes showing the highest specificity and accuracy are involved in the copying and expression of the genome. These enzymes have "proof-reading" mechanisms. Here, an enzyme such as DNA polymerase catalyzes a reaction in a first step and then checks that the product is correct in a second step. This two-step process results in average error rates of less than 1 error in 100 million reactions in high-fidelity mammalian polymerases.

how exactly does the enzyme copy and check?

Anyway, the fact is that if scientists understood everything about cells, they would have created one from scratch (directly from atoms) in a laboratory, and the cell would have lived. So far, it seems that they've succeeded in making an artificial DNA (this DNA was not invented by them, but it was made to be the same as a specific DNA, if I remember right), and have replaced a cell's DNA with that one. On the news (I had found an article then), in the same article, I found statements like "science has created a cell from scratch", "scientists have successfully revived a cell!" AND that "they replaced the DNA of a cell with another one" - all these three different things were said in the same news article! When it seems that the true story was that they replaced the DNA of a cell with a DNA made in laboratory.

Also, why do cells have a lifespan? Why do they not just... live forever?

If there are very simple answers to my questions, then sorry (I don't know too many things on the subject "cell biology").