Here's the photos:
from top - inner door pull with panel, and then that removed (just 'pops' off) to show Allen bolt.
The door release: more tricky - (to confuse, these three photos are upside down, but you'll get the gist) pull handle (as if opening door) and push a finger in behind the handle to pop out the little plastic cover. Release the handle and you'll see the Allen bolt through the hole the cover came from.
I imagine you will need to unhook the rod between the handle and the lock mechanism too.
Last photo: Set of pry tools. Made of nylon - very strong but don't mark the paint or plastic (so long as they don't slip). The clips are very stiff, and the door is lined with very thin polystyrene that punctures easily if the pry tools are not used against a solid metal bit.
There are seven clips - you can see them in photo 7 of this auction listing:
https://www.ebay.co.uk/itm/2014-Fiat-Panda-MK3-319-5Dr-Door-Card-Rear-Driver-Right-Side-OSR-2187627/254309572179?hash=item3b36081e53:g:9MMAAOSwqSRdOZ1t
My latest 4x4 has no rear speakers - previous two did. I have not noticed any difference in the sound (quality or volume) when sitting in the driving seat, but assume anyone in the back seats will?