I am always willing to help but not to teach. Here is many requests like: "teach me English/Russian/French" or any other language. But it is hard to teach if you are not a teacher. For example sometimes I do not know how to explain some Russian rules..I just know the right answer.

VERY GOOD QUESTION. YES, I LIKE TO TEACH MY MOTHER TONGUE TO FOREIGNERS, TO MY STUDENTS. ALTHOUGH I AM NOT A PROFESSIONAL TEACHER, I AM HAPPY THAT I HAVE AN OPPORTUNITY TO HELP THOSE WHO WANT TO LEARN MY LANGUAGE. IT IS CHALLENGING BECAUSE I WAS ALWAYS A CLASSROOM TEACHER, BUT I TEACH ONLINE NOW. 

However, I AM HAPPY BECAUSE I TEACH MOSTLY TO YOUNG PEOPLE AND I LEARN ABOUT DIFFERENT CULTURES, AND ALSO I IMPROVE MY ENGLISH BY TEACHING MY STUDENTS MONGOLIAN. I HAPPY THAT MORE AND MORE PEOPLE ARE INTERESTED IN MY LANGUAGE ALTHOUGH IT IS DIFFICULT TO LEARN AND IT ISN'T SO WIDELY SPOKEN AROUND THE WORLD. 

I AGREE THAT YOU LEARN ABOUT YOUR LANGUAGE MORE WHEN YOU TEACH IT TO OTHER PEOPLE. 

I think it must be interesting to teach our native language to a foreigner. Actually my native language (Persian)is not such a practical language in  all over the world so I haven't experienced it myself. Specially in this way I think we can know about the current phrases exist in the other language easily. In addition you can be more fluent in your native language about details that you didn't pay attention them before you teach it to foreigners.