I am currently studying while working. At first, I bought a book and studied on my own, but when I was about to finish the book, I came across this lecture on the recommendation of an acquaintance. I thought a lot about how I should know all this content while studying on my own. It is impossible, but I think this lecture completely resolved this part. I regret not having come across this lecture sooner, but I am grateful that I was able to organize the practical concepts, even if it was late. Thank you!