Many people think that if you are fluent in english you can teach it привести аргументы за и против этой идеи

I partially agree that a person who is fluent in English, can teach it. Good knowledge of the language is not enough without the pedagogical skills and capability to teach.

If a person knows how to read, write and speak English, he/she can share this knowledge and skills with some other people. They have to explain the rules of reading and how to make sentences in English. It is also possible to tell about the meaning of some words and expressions.

But any teaching requires some special knowledge and techniques. People go to special courses and institutes to learn how to teach. Only a certified teacher can do it well by using some course books, audio and video aids. Only regular lessons and the systemic approach can guarantee good results.