That's quite all right, we all start somewhere.

If it is an airlock, then hopefully it will have cleared itself during the engine warmup / cooldown on your drive home. In which case the coolant level would appear low this morning, and would need topping up.

You don't want to add neat coolant. You dilute it (instructions usually on the bottle) with water to the appropriate strength. I do believe you can buy pre-diluted coolant too, but not sure on that.

The symptoms you describe point to an air lock in the cooling system. Ideally, the air should be bled from the bleed valves in the system when the engine is hot and the coolant topped up as it fills the void from the displaced air. The mechanics who changed the water pump should have done what I have described and I suggest you take the vehicle back to them given the extent of your mechanical knowledge. You should do this sooner rather than later as it the engine needs to have adequate coolant in it. Bleed valves in Renault engines are usually located at the top LHS of the radiator looking from the front and in the heater hose in the engine compartment.