I just listened to what I thought was necessary. The lecture is very long, but I recommend that you watch it three times. At first, I didn't understand what was being said, and I wondered if I should keep listening to it, but the second time, I got a general idea of what it was. I think I'll understand most of it if I listen to it one more time. I've watched it twice, so I'll listen to it one more time. The pronunciation is a bit hard to listen to at double speed, and the feedback from community questions seems a bit slow, so it's a bit disappointing... Aside from that, I think you'll learn most of what you need to know about Spring Security if you study it with this. I recommend it!