Why automatically increasing volume up?

@michaelprithvi there are no easy or quick fixes. Since the volume increases, this seems to be an issue with the side button flex. I would start by replacing that flex. Now, since iFixit does not yet have a specific guide for that, use the one from here It was written in Spanish so use a browser that does the translating for you, if needed. Replacement flex cables are readily available at many sites and are really not to expensive.

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!