I've got this problem too. I think the newer versions of Unity (2017.3.0p3) and Visual Studio 2017 aren't playing well together. For some reason, I got past 101E, but am stuck at 210, the Gaze lesson.
I was trying to figure out what platform to develop for, and these lessons looked nice, but it looks like they may only work with older versions of Unity and Visual Studio.
I also encountered a problem with line 56 in the App.cs file
ApplicationView.GetForCurrnetView().SuppressSystemOverlays = true;
This gave a CS0618 warning that says it's obsolete. I replaced it with
ApplicationView.PreferredLaunchWindowingMode = ApplicationViewWindowingMode.Fullscreen;
I hope that part is right. I wasn't able to find any other question/answer anywhere that confirmed that.