Question

you've made a simple pendulum by tying a stone to a string.you want to reduce the time period.how will you achieve this?

Answer 1

The time period of a pendulum is a function of its length of string and mass of bob, as u cant edit mass of stone u can edit its length to vary time period

Answer 2

Shorter the length of the pendulum string shorter is the time period.

Hence you can reduce the time period of the pendulum by shortening the effective length of the pendulum.