Volume buttons are not working properly

@banothruthwik the very first thing I would replace is the volume flex cable. Since iFixit does not yet have a specific guide for this use soothing like this video Even so it does not specifically show how to replace the flex, it will at least get you into the phone and help you with the task. The flex cable is readily available at many online stores.

While you work on your phone, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has a device with the same issues as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.

Repair is War on Entropy!