Each class has different levels from the basics to advanced teachings. In general, each teacher performs a class starting from the basics, then introductory exercises, and then deepening the execution of the instrument. It is recommended to read the descriptions of each course to check the level as some are intended for initiated musicians and others for apprentices. Even so, each course is a very useful tool no matter what level you are. You will know the music from the experience of a master, which goes beyond a set of exercises.