It was really great that I was able to learn various knowledge about backend development (DB, API, SOCKET, Authorization, etc.). Of course, there were some difficult parts, but I think that learning this knowledge through online lectures and textbooks is like a shortcut. The development version changes every year, so there are parts where errors occur, but I think that you have to Google this much. And since the answers to questions usually don't take more than a day, I felt that they are constantly paying attention.