Sounds impossible ?
Easier than learning to drive a car ...
To learn to drive a car, you need to be able to coordinate several things at the same time,
and also learn driving rules and codes and laws.
In fact the first part isn't all that hard, the second is and most people, if they fail their driving test, they fail the theory exam concerning road signs, local driving laws and even explaining what parts of the engine do.
Well, if you already speak English, then you already know how to teach English.
It's like being born with a driving license, knowing all the rules, and also being able to physically drive a car. All you would need now, is the actual car, and maybe some petrol.
And in teaching English, the car is the course books, the engine is the way the course books have structured the teaching procedure for you, and the petrol is learning your way around the books and how to use the books and NOT the English language which you already know.
This is why, most people don't know that they can already teach English, because they believe that they have to learn grammar rules, and then also to learn how to teach them.
The course books New English File and New Headway, already have the grammar rules incorporated in the gradual progression from unit 1 onwards, and all you have to do is to learn how to best use the books, and also a few but very important aspects concerning teaching students.
So our course doesn't teach you to speak English, which you already do, but in three hours we teach you how to drive a Ferrari, in the form of English language course books and how to use them.
You already know all the laws and rules, even if you don't think you do.