After todays shower I decided to give it a try and it wasn't difficult at all... The bottom part of the back rest can be pulled out and it's only on place by a seem into a plastic kind of track after unfolding the leatherette it can just be pulled upwards and it gives enough access space to maneuver around .
My problem was that the rivet holding the lumbar support on place of the tracks popped out
I just Re-accommodated the assembly of the lumbar support back on place and its back to serve its purpose until I get a rivet gun and replace the broken rivet