So how did life begin, the "spark" of the big bang.
By not doing so.
There was no life at the time you are asking about.
What was the first life form, that finale evolved into humans?
Primitive, pre-cellular organisms.
You say humans evolved from apes, apes evolved from something,
and that evolved from something, all the way back to first life form.
Nobody does.
Humans ARE apes. We are apes, the way Toyota Tercels are automobiles.
There has to be something that started it, if not God of Abraham, then what?
Since you are reaching back to the initial expansion of the universe (the Big Bang)...
Try thinking in terms of forces, not life forms.
Gravity.
Centrifugal force.
Momentum.
Pressure.
The original singularity, bound by gravity, spinning rapidly,
At some point, the mass of the singularity becomes unstable... and overcomes gravity.
The resulting release of energy, is the newborn universe.
Energy cools to become plasma.
Plasma cools to become matter.
Matter cools to become electrons and protons...
... which cool to become atoms.
This begins the atomic phase of the universe.
Still no life.
For at least another billion years, the universe will not have the heavy atoms needed to form complex carbons.