You undo the two screws and the saddle will pull off the pipe in two pieces.
However!
There will be a hole in the pipe so before you start make sure the mains water is turned off - you can double check by flushing the loo and make sure the cistern doesn’t refill.
You could then cut off the pipe just below the hole to remove it and reattach the push fit connector to your pipe. However with all that paint on everything I would either leave it alone or cut the lot out and repipe it in nice clean copper. Or if you are not able to do that , you could buy a new flexi connection to the loo and this could be attached to your existing pipe if you clean off the paint first