Scientifically, what do you think happens when you die?

Your relive your whole life before your eyes as you're dying. You feel at peace momentarily and then become non-thinking ash particles. You relive from dirt to bacteria to tree... Yet tree leaves fall and die and become dirt and bacteria and evolve eventually into animals... Meanwhile you as a tree are no longer just the tree but all these animals that are evolving around you. You become the whole world eventually but then you don't know what organism you are because you are just all these plants and animals living together... So you call yourself life

Why don't you go die and tell us?

"Time" stops at the point of death, that's how. Time is a construct of consciousness, the moment before you die your brain "slows" time down to eternity and you start a new dream life. You die in that life, time stops for you, than you're reborn into the next life again. 2 min. in a dream can feel like hours, your brain obviously is what constructs time

Shortly said, the question is when begins and ends the consciousness.
If it's with the brain, then there's nothing before or after.
If it's not, what is it before our brain appears (why don't we remember it) ? And what does it become ?
Sadly, we don't have a fuckin idea about it.

Time is a universal constant, it encompasses everything quantifiable in our universe.

Even inanimate objects experience time
Such as the degradation of iron due to the process of oxidation over TIME.

In order to dream, you need concsiousness, because dreaming you are uncsiousnes, so therefore we can conclude that in order to be unconscious (dream life as you said) it would require consciousness, which is impossible if the brain is destroyed, what about if someone got shot in the head and their brain matter was dispersed everywhere.....

Nope. Time is not a sure thing. read about loop quantum gravity, you'll understand

Ill check it out.
Any good books on it?

You are instantly revived virtually in a heaven or hell created by future lifeforms.

Have one, but in french. Might exist in english, as it was written as an introduction to the model by its main author : Carlo Rovelli. Roughly translated, it is "What if the time was not real" or "did not exist"
A pretty intersting and easy book about the author and the theory

Time is a universal constant? What happened to special relativity?