Have you not heard of the Miller Experiment?
Happened way back in the 1950ies

https://en.wikipedia.org/wiki/Miller–Urey_experiment

It shows how mixing chemicals can form the blocks for life

Others have shown how chemicals come together naturally to form the first steps of what could become life.

Interesting reading of all the different tests and experiments.

And now that we have been able to study vents at the bottom of the ocean they have found low temperature vents with the necessary chemicals to form the ingredients for life

You and I may have to rely on words on paper as I at least do not have the training or desire to go searching myself but fortunately we do have scientists that are working on the answer but we may never know how exactly it occurred since it was many many years ago.
It is not impossible that several different forms of life began but only 1 finally became successful enough to evolve into all the forms we see now on the Earth.

So we have the choice to accept what experts in that field of study have concluded or just say I don't know and continue our life.
I am curious so I keep reading about any new finds.

I hope you at least know and accept that it took many many years for the first crude forms of life to evolve enough to crawl anywhere.