classes:  lecturer. His teaching style is difficult to understand, there are no preview materials for students, he does not give students an overview of the subject that makes it difficult for students to absorb.  curriculum. His teaching style is difficult to understand, there are no preview materials for students, he does not give students an overview of the subject that makes it difficult for students to absorb.  facility. His teaching style is difficult to understand, there are no preview materials for students, he does not give students an overview of the subject that makes it difficult for students to absorb.  general. His teaching style is difficult to understand, there are no preview materials for students, he does not give students an overview of the subject that makes it difficult for students to absorb.