There is much to say about this! But I am constantly bemused by the Scholars who state that theorising on existence before the Big Bang, is a pointless exercise prior to the existence of time. And there are many opposing theories as well.
I think that if we are ever going to understand the laws of the great machine that our perspective reality exists within, and thus all other dimensional perspectives, to extend ourselves from a Law of General Relativity, to one of a Unified Theory of Perspective Relative Reality, our limited comprehension of the deeper areas of physics will remain unobtainable to us.
At the point you feel you are going mad picking through the geometries and maths of eleven dimensions, and their relating models, you need to step back.
TIME ITSELF IS ONLY AN OBSERVATION OF PERSPECTIVE EXPECTATION, WE HAVE CREATED, RELATIVE AS WE SEE IT ONLY TO OUR REALITY.
The fact is this `machine` is moving and we appear to exist, so to try and find peace in the answering of the `before the before` question we may have to consider that our concept of time ( an therefore space ) is fundamentaly flawed, and proving how we exist within our reality at all is surprisingly hard!
Understanding what this means on a Quantum level is still confused from a Quantum point of view ( no surprise there! ) But Time pre Big Bang, as we observe it, was probably preceeded by an altered state of the same process of progression and regression. Little consideration is givin to what our universe expanded into, or to the possibility that we are a Universe within a Universe.......? Our inability to feel Time as anything other than non linear is a genetic `hard-wired curse`, backed by information supplied via limited senses.
In terms of the Universe on a level of its Quantum Energy State that all matter is made from, the past present and future all occupy the same space in space/time.
Enough said! I`ve tried to be general, and keep the tech to a minimum otherwise it becomes an impossibly large subject. I do not have the answer, but we need better theories in physics there is a shortage!
My answer endeavours to encourage you to look wider, sometimes where there is no rational answer, just because it does not appear to be the way, it does not mean it can`t happen.