I want to recommend you to try taking a class with this teacher. The reasons why I think so are:
1. He didn't overlook some mistakes that I made and never pretended not to find, and he tells me. So I could realize my mistakes, and improve my English Grammar skill.
2. He never stop smiling even if I made mistake. So I could feel relief during my class with him.
3. He made the most of chat. He wrote my answer with some revisions on it. I can review my answers and my mistakes anytime.