How can we stimated Scalers in General relativity theory and affine space?

I can't find it in my country all books are for amator physicists (introdaduction to general relativity... ) I need a powerful book with equations and answers and tensors...

What happened before big bang that we have a big huge explosive for the begin of the our world?

How and why mather make flat space curved curved?
How we can calculus lorentz factor for curved space?