It is highly recommended for actual development. This is a lecture that I used as a reference while quickly creating an Android app with only JAVA knowledge. Although errors occur occasionally during the lecture or time is wasted due to running the emulator, for people like me who have no experience, the lectures are easy to follow for actual development and I think I was able to easily deal with the same problems. I have now reached the commercialization stage of the bus app, but if you have additional knowledge of FireBase or BackEnd, I think there will be no problem in developing most apps.