Heres a set of pictures depicting the problem.
Any form of help will be much appreciated !!!
Your best option is to take the phone to an Authorised Motorola Service Center to get it repaired, but it may be possible to attempt it yourself.
As there are no iFixIt guides available currently, your only other option would be to refer to
videos a video on YouTube, where the screws on the bottom of the phone are removed to access the internals (and volume button)
I suggest you don't try to fix user self-take it to the service center and make it be fixed because if you fix it won't be the longer best way is to take it to the customer service center.