What would be the best way to take what I know from b1 and apply it to s4hana
S/4 is very very different from SAP Business One. You will only be able to use the most general ERP knowledge learned from B1 when working with S/4. The main difference is that, generally speaking, S/4 will contain a varying combination of modules, each of which handle an aspect of a larger business. B1 is a single software that handles all aspects of a smaller business.
The HANA database system is the same for both S4 and B1. What ever you know about HANA will serve you well when working with S/4 HANA.