Questioning my German Skills

Ok...so leading up to this very moment I thought I knew some German.  I was not 100% confident in my language skills because let's face it, there is ALWAYS something for me to learn.  As of today, I really feel I have studied in vain.  The 3rd year class is doing presentations on various works selected by their teacher.  Many of them have asked for help on some of their articles, which I had did not have too much trouble answering.  One particular group came to me for help with the first chapter of a book.  I was completely floored by the chapter.  Not only could I not answer their questions, but I also couldn't understand the overall plot.  I decided I would take a copy home with me to work on, which needless to say was a mistake.  I stayed up until 2 am this morning reading and re-reading the chapter.  After the 3rd read, I finally got the gist...ONLY the gist.  Once I got involved and felt like I was understanding, I couldn't stop reading it.  As I rode the subway to class this morning, I re-read the chapter again.  It is now 10 minutes after 3 and I have spent what feels like the past 2 days trying to comprehend.  After yesterday's lost adventure and my not being able to understand this book chapter, I am really feeling like a let down to the students.  I have helped the group the best I could and have tried to give them as much input as possible but man oh man....I just really hope they do well tomorrow.  They have to ramble about this author and this chapter for 15 minutes IN GERMAN...I will just have to keep my fingers crossed that I didn't let them down or steer them in the wrong direction...check back in tomorrow to see how it went...