Well, take it easy and go slowly.  For now, you just need to understand stuff shallow, just a rough picture of the functions I am writing.  As I suggested earlier, you might, as we go along, convert my FP functions one by one, to your OO methods.  

And as the saying goes, eat the big elephant bite by bite - First bite is SPI setup, Second, nRF24 initiatization, third, nrF24 configuration, ... 

This way you taste each bite slowly, understand and enjoy, ... 

I am a huge fan of the mad electrical engineer Oliver Heaviside, and agree very much what he is saying: "Shall I refuse my dinner because I do not fully understand the process of digestion?" https://libquotes.com/oliver-heaviside/quote/lbo4z9d.