"Vocab. 1" - too much new at once
Maybe it's just me, but I feel like there are too many prefixes introduced all at once in "Vocab. 1".
It is a lot of new material in one lesson for a beginner. One strategy to cope with it would be to only focus on a few and just use the hints to supply the others when you are answering questions. So you decide how many you can learn at one time and which ones you want to know first. Just try to memorize those and not use hints for them. Use hints for the others. As you do the course, gradually add a couple more at a time when you can handle it. In the meantime, use the hints as a crutch for the ones you don't know.
Another strategy would be to study the prefixes on your own for as many days as you need until you feel like you have them mastered. I learned some key ones that I felt were especially significant first and then the others sort of fell into place around those. I did have to look up the ones I did not learn as well for awhile. But having a few really solid in my head was better than only sort of knowing the whole group. I really recommend focusing on one or more at a time instead of all at one time.