remove all the plaster gypsum boards and frames of ceiling
attach/stick firmly and cover all the ceiling with a layer of 2mm or 3mm MLV sheets directly to the ceiling
then build ceiling stud, fill the stud space with rockwool 50mm 60kg/m3 mineral wool at least
then use 9mm at least gypsum boards to cover ceiling stud
then a layer of MLV again attached to the gypsum board again (ensure it is firmly attached and wont drop)

then build ceiling stud again, but this layer leave it with a gap of 6 inches at least with above, fill the stud space with rockwool 50mm 60kg/m3 mineral wool at least again

then use gypsum board to seal the ceiling as per what you have of your ceiling now

floor to plaster ceiling is 10ft. old school unit is 9ft.
floor to RC ceiling is 12ft. so you have about 2ft (30cm) room to play with.
by doing that, you can reduce about 20db-30db noise from above.

2ft = 60cm
typo

so the same thing to the wall. a layer of MLV attached to the plaster cement brick wall, then build a wall stud, fill the stud with rockwool, seal the stud with a layer of gypsum board.
of course you will still hear noise if the kid purposely knock the wall but it will be compromised and feel the noise a bit more denser.

MLV sheets 3mm cost about rm10 per sqft
Gypsum boards 9mm 4ftx8ft cost about rm0.625 per sqft
Rockwool 50mm 60kg/m3 cost about rm4 per sqft
Pine wood 1x2x6ft cost about rm8 per piece

Calculate the material cost your own. Of course it would be much more cheaper if you purchase your own but provided got someone wanna do it for you.