What are the requirements for a good calligraphy teacher? I hope I can learn something real, thank you in advance!

Solid basic knowledge of calligraphy, accurate structure analysis, appreciation analysis, profound cultural background. Writing a good hand is a skill, and calligraphy is an art, depending on what you want to learn. It takes experience and accumulation to reach the artistic realm, so appreciating more good works will improve your aesthetic view, so that you can move towards art! Good luck!