This... altered view on reliving one's life is, well, quite interesting. So if it were true, I could very well be on my second or billionth life but most certainly not my first, as evidenced by the mere existence of the deja vu phenomenon I've encountered.
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Quite contradictory if you ask me. It's very interesting, though. Your ideas had my mental gears a-running.

Now, dream. There is a theory that dreaming is like a survival strategy machine where the mind tries out random possibilities and attempts to predict the outcome.
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True enough, we have; what is eerie is the accuracy of that dream owing to a conversation we have unknowingly overheard.

That happened to me everytime, but now it happens less since I'm growing bigger...
I trying to practice it these days but i don't see any better results.
I had no idea why that happen

For example, you could very well be in a classroom listening to the teacher. Your conscious thought is focused on the lecture, effectively overriding other stimuli from leaking into your conscious thoughts. However, it could very well be that you are overhearing talk of something, let's say a hotel lobby. We could very well be unconscious that descriptions of this hotel lobby is secretly being encoded into our memory. Indeed, we'd have no idea of it since our mind is pre-occupied with this lecture.

Now, dream. There is a theory that dreaming is like a survival strategy machine where the mind tries out random possibilities and attempts to predict the outcome. We all know nitroglycerine is highly unstable but ever and anon, we may dream of ourselves, or someone else, shaking nitro and ending up in fine pieces. This is how the mind, through simulation, re-affirms that nitro, indeed, is dangerous.

Sometimes, the dreaming mind might retrieve from our memory something we are not aware we know, like our hotel lobby, for example. From this stealthily encoded data, our mind could very well conjure us a scenario where we'd be in this lobby when the bomb goes off.

Now, let's say you have finally made it to the hotel in question. Entering the lobby, we'd get that strange feeling that we have been here. In reality, we have our suspicion that we have dreamed of this. True enough, we have; what is eerie is the accuracy of that dream owing to a conversation we have unknowingly overheard.

Then again, it could just be the Matrix reprogramming something.

i read somewehere that this regards in our past life. Our life before we exist had been on those places that you actually felt the dejavu ..

sorry, but I don't agree. For example, if in my previous life I was a bug, how would the situations I feel deja vu in now, such as walking along a part of a street or past a certain person take place, since a bug has a really different perspective, different view of "seeing things" and massively larger sizes of everything - just doesn't seem to be a valid argument... sorry !

That said, it just may be that time isn't the journey from past to future that human consciousness makes it appear to be - perhaps it's more like a field of endless possibilities, where all probabilities are possible!

And that said, just perhaps, what we call 'deja vu' is not even remembering the past or future, but instead perceiving an event from another possible past or future, a perception of a random event plucked by random probability from the sheet of time.

thank you
the term "deja vu" mean : already considering