There really is no such thing as "death". It's just a descriptive state of matter, energy, and space. Even after being declared dead, you are still composed of all the atoms that you ever had. Your brain pathways have stopped transmitting, but they are still there.
Once your atoms disperse, they become something else in the universe. Matter cannot be created or destroyed, it just changes forms.
Medical personnel have tried for thousands of years to define death.
Is it when the heart stops beating? No, because we can now keep you alive after your heart is worn out and can even transplant a new heart.
Is it when you stop breathing? No, because we have machines that will breathe for you until you get a lung transplant.
Is it when your brain stops thinking? No, because your body can still be alive in a vegetative state.
Is it when you are buried, cremated, or shot into outer space? No, because your atoms still exist. They just decay into different forms.
Do you "go to heaven"? No one knows, but where is it? No one knows.
Are you just not "you" anymore? Perhaps, but again, no one knows and your atoms are still part of the universe. They cannot be destroyed.
The only way to find out what happens after you "die" is to do it yourself. And then, in spite of rumors of life after death by magical gods, no one has actually come back from "death" to let us know.
You may "believe" Jesus or Horus or some other god did, but there is no physical proof of it. It's just rumor and rumors of rumor. There is no actual physical proof of an afterlife, heaven, hell, or coming back from total bodily system failures.
Once you are "dead", that is it for you. So spend you life like it is the precious commodity that it is.