Cracking a CHAP from Freeradius
#21
There is no easy and quick generic way to learn things like this. It's knowledge you amass over months and years by reading, observation and experience, combined with a fair amount of common sense.

In case of hashcat the wiki and forum are valuable resources. For generic knowledge about cryptography and computer science wikipedia is a nice place to start (although it may sometimes be too technical for a beginner).

Be curious and read articles about whatever seems interesting.
#22
Also a good idea is to read the RFC docs , even if they are not easy to understand. They are our basic docs if we add new functions to our tools:
https://tools.ietf.org/html/rfcXXXX
where XXXX is the RFC number of the doc
for example:
https://tools.ietf.org/html/rfc3579