I'm not here to tell anyone how to navigate through this site or when to move on to the next lesson but what has worked for me taking Lisa's lessons is don't jump ahead too fast before you got something down pretty good. I was doing the songs with the chord changes, Roll like water, I get it now, Skeeter loves Amy and Darling Destination.
I wasn't quite getting the changes on time with the first two songs after awhile so I got bored with them and I added the other two. So now here I was playing four songs and none of them very well. Just over and over again with them sounding pretty bad. Of course there were some good times, but mostly bad. So I decided to just keep playing the first two songs and nothing else until I got those changes down just about perfect. Now I feel much better about my playing that I have those in my back pocket now and can, in my opinion rightfully move on to the others. This works so much better for me than trying to get the changes down to a bunch of songs at once and not really getting anywhere. Your opinion may differ but this is what I found has worked best for me. Taking it in little pieces instead of big chunks just so you feel better about moving through the course. It's a journey.