The question is in Avot. One who learns to teach is given to learn and teach. One who learns to do is given to learn teach and do.

I think that mishna is hard to understand.  I can see the advantage of teaching Torah and also of doing. From what I remember the Gra brings a source for that mishna that might explain it. My thought is Torah has to be learned in order to do it. But what if one has sinned and caused others to sin? Then one needs to do and to learn and teach also. I am not saying this explains that mishna.. I will have to think about that mishna.

 It is connected with the mishna that anyone who is מחטיא את הרבים אין מספיקים בידו לעשות תשובה. anyone who causes the many to sin is not let to do teshuva (repentance). I was surprised to see some books of Musar [Mediaeval Ethics] that I respect bring this down. The first place was in the חובות לבבות. And then Reb Israel Salanter in his letter of Musar and then in the Madregat HaAdam by Joseph Horvitz from Navardok. They all bring down this problem that once one has sinned and caused others to do so he can not do repentance. But then they give a solution to the problem.  המזכה את הרבים To bring merit to many. This seems to me to be very important. It is giving a solution to a problem which seems in solvable. If one can not repent on his sins what hope is there for him? But then they bring this mishna that if one brings merit to the many that serves as a way out of the problem. I think Bava Sali must have been thinking along these lines also. He was once saying words of Torah and it was after the time for the generators to go off line. People were getting ready to leave the hall. He said, "As long as words of Torah are said here, the lights will not go out." And that is what happened. Thus, I see teaching Torah as a way to come to keep Torah.

What is the kernel of what I am saying is that I think that sins stops one from seeing the light. They cause one to  lose the way, and think evil is good, and good is evil. Thus, after one has sinned, and especially caused others to sin, it is virtually impossible to repent. Because if he tries to repent while thinking what is evil is really good,- then all the more he repents, all the more sin he will be doing.

The best advice is thus to learn Torah, with the Avi Ezri of Rav Shach and Chidushei  HaRambam of Reb Chaim from Brisk in order to get an idea of how to understand any given law in the Torah.