I worked as a waiter in a hotel, and the manager asked someone to be my teacher and let her teach me, but she only taught me some basic things and said she wanted me to watch her do it myself.

In fact, this is not a technical problem, but a problem of dealing with people. First of all, you must respect your master and endure with him no matter what is wrong, because as the old saying goes, you should be a teacher all your life, be kind to your master, and learn various skills quickly on this basis. A hotel waiter can't do it. What else can you do?