Started Spanish in University

In January I started the second half of a beginners Spanish class and I'm surprised how much has already been covered in the class. The professor said that in the first half they had gone through what is the equivalent to the amount of Spanish a student would learn in all of high school. That's in only 3 months. I am not finding this difficult though because I have learned a lot of Spanish on my own but I can understand why it seems like quite a challenge to other students (and it doesn't help that the professor confuses people somewhat often - for example the way he explained the pretérito vs. imperfecto de indicativo: I actually lost marks on a test on a question or two where I would have used the preterit before joining the class - before listening to the professor try to explain things, but he confused me and also lead the students to believe that the pretérito and imperfecto de indicativo are actually interchangeable much of the time, ["it's up to you, you can use either" for an entire set of fill-in-the-blanks he presented to us and that there are situations where using the imperfecto de indicativo may add more "feeling" to a situation where you could also be using pretérito.]) Honestly I think I will just use the knowledge I have from the grammar books I have gone through. I still got an A+ on that test, which I didn't study for, because I didn't think I would have to.
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Also, I'm almost done the book called "The Spanish Subjunctive Up Close" which is helpful but I will probably want to go through it again. I think I'll feel more confident after going through it twice.