The lecture content is explained well by selecting only the key points. It also matches my learning style, so I purchased and listened to the following lectures. However, there are some parts of the content of this lecture that are the same as the videos of other lectures that I will learn later. Because of this, when I listen to this lecture, there are some parts that talk about things that I did not learn as if they were taught before, which can be confusing. I understand that it is essential to explain the content for establishing concepts, but It would be better to record it separately and make other videos that are more appropriate for the situation, or to allow students who have completed this lecture to listen to other lectures that have overlapping content by deducting the price. If I had known that the same content would come up twice, I would not have paid for this lecture and started listening to the following lecture right away, but I can't help but feel like I paid twice because I didn't know and paid for it.