Radiator coolant, please use proper one, you can buy in kiosk,
if you keep putting water, aiyo, water is not a coolant hor, it
will boil very fast and heat up the engine part + vaporise easily,
and it will also rust your radiator due no oil base coolant.
Remove all yr water at the radiator base knob, close it back and
add coolant (water mix with coolant base)...mostly greenish in
color. That will be what workshop in cdg doing if you send to
them.
When topping up, try to use coolant and not water, if coolant
after top up, slowly can see small bubbles, it mean radiator
leaking.