Not bad. I have taken online courses and given face-to-face lectures. After listening to the free class, I signed up for class. The head teacher is very reliable and basically responsive. The teacher is also humorous and inflexible in class, which allows me to grasp the memory of the class, so I can remember the content of the class after class and just go home to review. If not, you can call the teacher to ask questions after class. . The teacher is also very enthusiastic.