I have simple pendulum related questions:

1. why does time period of pendulum does not depend on mass
   1. if mass of bob increases then the ossilation from central point- i mean the distance how far the bob goes changes, or it remains same and the speed changes to make time period similar, i hope you understand what I want to ask.

A very loose answer would be that the time period actually depends upon the angular acceleration and not the torque.Just like the time taken for a object to fall through a height of h, depends on the gravitational acceleration and not the mass, i.e. if you drop a sponge ball or you jump yourself, you both will cover height h in the same time(of course neglecting air resistance).Similarly, the time period of a pendulum doesn`t depend upon the mass, or rather the inertia of the pendulum, but only on the angular acceleration due to gravity.Now you might ask that in this case, it should also not depend upon the length, but the term of length comes when you calculate the angular acceleration due to the acceleration of gravity.