don't fret. No all or nothing thinking.

it's ok. see? you have read and studied the intro econometrics for only two days, and now you at least can understand what's going on in the econ 599 advanced book. so it worked! even though there are a lot more estimation materials that the intro book didn't cover. but at least you are much less confused than when encountering it for the first time.

So, keep going! don't get upset! if you stop, you will for sure learn nothing! he doesn't test on everything, so don't fret if you can't understand every single details. just learn the majority.