For engineers moving from LTE to 5G, I have found that theory alone does not help much. What works is following one procedure end to end in real logs. This is the order I would suggest:
- 5G SA registration and PDU session setup. Follow RRC setup, NAS registration, authentication and PDU session establishment in the logs.
- NSA vs SA. See how the UE behaves in each mode and where the signalling differs.
- Mobility. Handover and measurement reports, and what a failure looks like in the log.
- Interfaces. Learn what F1AP, NGAP and E1AP carry, since many real issues show up there.
- O-RAN basics. RU/DU/CU split, 7.2x open fronthaul, M-Plane, and the roles of RIC and SMO. Then PTP and SyncE for timing.
For tools, QXDM and QCAT are the standard way to see these procedures on the UE side.
Live batch that follows this same path with QXDM/QCAT log analysis. Details here 
: LIVE DEMO: 5G In-Depth & O-RAN Detailed Course*