If the instructor is like me... He'll assign you a few basic things to work on. All of which, you can't possibly master in the time given. As an instructor it's imporant to find the balance between challenging a student and pushing them too far. Every student is different. Some students come in with a burning desire to learn to play and they won't put the thing down... This kind of student will generally learn at a more rapid pace... Then you have students that don't really want to be there in the first place... but either their parents or someone else paid for the lessons and is forcing them to get their moneys worth... These kinds of students generally don't advance as fast because their dedication falls short. When beginning anything... it can get frustrating... Everyone learns at their own pace so work on all the material that your instructor has given you and get as far as you possibly can... I would like to think that your instructor wouldn't expect you to have mastered the chord changes and the riff he assigned you.... He/She is probably expecting you to have a good grasp on how to make the chord changes and be in a position so that they can show you further how to perfect it. If you get it down perfect... that's awesome! But don't think that if you don't grasp something right away you're not a good guitar player... Because everyone struggles in the beginning. Just approach it with the mentalitly that if you don't practice you're not going to to get any better... Basically just practice as much as you can and you'll be just fine.