A person who is fluent in a foreign language can easily teach it

Many people think, that if they know foreign language well, they can easily teach people. I disagree with this opinion, because good knowledge isn’t enough to teach other people and some people haven’t got a talent to be a teacher. There are many people who think that if they can speak in foreign language well they can possibly teach it, because the main is knowing language, but I think that first of all they must learn how to teach and then teach other people. Teaching needs a good education. Only real teachers with professional education can manage the knowledge.