So in Day 2, we start by looking at the other language feature we need in order to really do anything: flow control. That's all fairly straight forward. You've got your while, your for and your if...then...else.
The third section, Reflection, is also fairly straightforward. An object can look at it's own slots, and the slots of it's ancestors.
I don't want to say the middle section, Messages, was confusing, because it was more like totally opaque. It's not so much hard to understand as I just don't get what the big deal is. Which leads me to suspect that I've missed the point. I expect I won't really understand it until I get through doing the self study exercises. But that will have to wait until tomorrow.
The one other thing I learned today, is that an hour is not really long enough to make much progress. At this rate, it's going to take at least a couple days to make it out the other side of Day 2, and I expect Day 3 will take even longer. So this might not be so much Seven Languages in Seven Weeks as Seven Languages in Several Months.