The question is, what was before Big Bang 13 billions years ago.. I know that Big Bang is questioned as a four-dimension fact. So time was one dimension and it was created in a moment of Big Bang. There is also bran cosmology that describes alternatives, but i know just that from wikipedia. Is there any eager to answer me simply, what was before? Or, if universe started with its time-dimension, so when something starts, then should end, so what would happen if it ends. If the answer is, we don't know what was before big bang and don't know what would be after time finishes? It's quite complex.
Big Bang is a highly speculative event, more precisely: Big Bang is a limit point of the standard model of cosmology.
Until now Big Bang is not part of any accepted theory in cosmology. The reason is that Big Bang is a singularity of the standard model: Physical quantities like the energy density of the 4-dimensional spacetime tend to infinity when moving backwards to Big Bang. At this point we leave the domain of validity of the model.
In the standard model the question “What was before Big Bang?” is meaningless because there is no “before”. Anyhow it is possible that our universe will end in a Big Crunch after contracting to a singularity.
As alternatives to the standard model several models are discussed which avoid an initial singularity. Such models consider a series of cyclic universes.
For a popular presentation see “Martin Bojowald: Zurück vor den Urknall (German)” or any youtube video based on quantum loop cosmology.
Kant wrote about this question in his "Critique of Pure Reason". The first antinomy of pure reason is exactly about this. With a proof by contradiction he tries to prove that the world must have a beginning. Also (this is the mind-boggling part) he proves, that the world can not have a beginning. His idea was to show, that we are simply incapable of dealing with that question. Why is that?
If you are a Christian you might believe that in the beginning there was the word. If you are a scientist you might believe that in the beginning there was the Big Bang. Either way, the very concept of time demands that there is something that happened before: God thought that now is the time to say the word or a quantum fluctuation happened. So if you are trying to grasp the beginning don't think of the word, don't think of the Big Bang, don't think of all the stuff that happened before that, think of the beginning. Are you there? Did something happen before the moment you are thinking of?
If "yes": Something happened before the beginning?! You are doing it wrong! Think of the beginning!
If "no": What was a second before the moment you are thinking of? It doesn't matter how you answering that question. Even if you say "Nothing" you are admitting that there was a second before the beginning. You are doing it wrong! Think of the beginning!
Kant's point is: It really doesn't matter what you are thinking of when you think of the beginning: You are doing it wrong! What you are trying to do is applying concepts that are valid for specific entities (like the earth, the sun, your parents) to "everythingness" (i.e. the universe) itself. It does not work, you will always fail. We are at the limit of what we can know. Beyond that we cannot know anything.
 It does not help if you say: "Well, that was before time began". There was a "before"?!. You are doing it wrong!
If you accept the idea that the universe started with time and not in time then "the question 'What happened before the big bang?' is meaningless." - see this article by Paul Davies
Swami Vivekananda speaking in the late 1890s said - "We believe in nature being without beginning and without end; only at psychological periods this gross material world of the outer universe goes back to its finer state, thus to remain for a certain period, again to be projected outside to manifest all this infinite panorama we call nature. This wavelike motion was going on even before time began, through eternity, and will remain for an infinite period of time." The Complete Works of Swami Vivekananda, Vol. 3, p. 374.
There were an infinite number of universes before and there will be an infinite number of universes in the future. There is no creation per se. There is only projection.
According to modern physics, the universe started with a point of Initial Singularity with a Bigbang explosion and there was no spacetime beyond it. Hence we don't have absolute dimensions Time and Space to measure/understand beyond Big Bang.
There are some theories which describe the state and source of initial singularity. These theories are being developed in order to explore the possibilities of any entity of existence beyond Bigbang.
Case 1: Non-existence to Existence
In the case where point of initial singularity got self created from Non Existence (NE), then the chances of self-creation of point of singularity from NE outside of our universe is infinitely high (our universe can be considered to be covered by NE all around), hence the chances of such huge explosions like Bigbang would also be very high. However, no such phenomenon has been observed yet because such a massive explosion would definitely create a sort of havoc in our universe. Fortunately, this possibility has not been predicted by many physicists as it does not provide any strong reasoning behind it and it also lacks the description of cause/source of initial singularity itself.
Case 2: Big-bounce (Big-crunch) Quantum fluctuation
This theory predicts that our universe will end up by opposite phenomena of Bigbang and it will shrink down to singularity again known as Big-crunch. Once our universe will expand and reach upto a certain extent, and then the process of contraction will start eventually reaching to point of singularity again. Accordingly, the earlier Big-crunch’s material from the previous universe was the source of matter and cause for initial singularity. According to this theory, there must be a change of state of existence before our universe was born. It leads us to consider the infinite cycles of Bigbang and Big-crunch happened earlier. So some absolute dimensions are required to measure those cycles of existence because current spacetime dimension cannot measure that part of existence.
This theory also suggests a different view that there may be a potentially infinite number of parallel universes in the disconnected timelines, this creates the possibility of multidimensional time in which other dimensions of time can sometimes interact or merge into one but we may not have been able to observe it yet. These multiple universes could be the cause of initial singularity. Here again, we need the absolute dimensions to understand and measure that part of existence because these imaginary timelines are not yet well defined to measure Existence.
Case 3: Initial Singularity existed infinitely
The third possibility is that the initial singularity was self existing infinitely without any external source and any previous universe/multiverse. The initial singularity itself was the source of all material of universe and nothing existed/existing outside of that. So the question arises: whether there was a change of state in the initial singularity or it just remained in a particular state of existence?
If the initial singularity remained in a particular state of existence and there was no change of state, then there must be an external cause (it could be a wave or particle or anything which we don’t know yet) for Bigbang to occur because no change of state was happening inside the initial singularity. Initial singularity should have remained in that particular state of existence infinitely, it could not explode unless any external cause interacted to it. Hence we must agree that there was a cause outside initial singularity, let say it was “Cause X”. This Cause X can be considered as infinite in nature else we have to consider another “Cause Y” for this “Cause X” to occur and so on. These mentioned Causes must be considered as part of existence according to our definition of Existence. To measure that existence, we need some absolute dimensions because that part of existence is outside of that initial singularity where spacetime dimension did not exist.
And, if the initial singularity was in a continuous change of state of existence since infinity, then we can consider it as a valid reason that nothing existed outside. This is also a valid justification for Bigbang to occur due to internal cause. Once again, we need absolute dimensions to measure that change of state of existence for initial singularity.
Considering all the above cases for the description of initial singularity, we can conclude that:
The Bigbang explosion is certainly not the start of Entire Existence however it could be considered as the start of our universe only. There is an infinite chain of causes behind the big bang which could be anyone of the above mentioned theories. These causes must be considered as part of Existence as per our definition. The initial cause of all the causes and the initial source of all the sources is still very far from us to be understood.
Results from the above discussion:
• There is an Infinite Existence beyond Bigbang explosion and initial singularity.
• Bigbang is a part of Existence and the cause/source of Bigbang must be considered into account for further exploration of Existence.
• There are currently no dimensions available to measure the Existence beyond initial singularity (imaginary timeline which is not well defined to measure existence and spacetime does not exist beyond it).