Grammarly told me you should get rid of all commas. Like:

"After her parents' tragic accident, a young woman discovers a secret in her grandfather's diary that goes back to a quantum physics conference in 1927 that could not only change her view of death but also save her terminally ill brother."

I, indeed, don't think it gives you enough breathing space reading it without commas. You could just play around with Grammarly free online grammar checker. This was the best solution I could find right now.

Thanks everyone ....