The key to the chapters you don't understand is the chapters you think you do. Become a better person and the meaning of mysteries will more easily yield to your efforts to unlock them.
A key: any remaining facets of a mystery you are trying to investigate are strong evidence that the part you think you have figured out is wrong.
God solves the whole puzzle, and the more of the puzzle that remains, its geometrically more likely that you are further off than you think.
This video had some related points.