Summary: There are two questions. The first question talks about the conservation of energy and how the length of the string relates to the total energy of the system. The second question is elaborating on the frequency and period of the pendulum.

https://blogs.ubc.ca/phys101/files/gravity_forms/1-72f8f8fec225ededbd95c074100f3d9f/2015/02/download.jpeg