A310 overtemperature

Dear friends
today something strange happened: I did some km, when I returned to home the temperature watch was at 90° but tank of cooling water was in overpressure and car loses a lot of water...please can you suggest what can I check?

[Alpineandy]

The same as any other car.
It could be an air-lock in the system, a leaking hose, the thermostat, the radiator, water pump or a head gasket.
Just check them in the same way you'd check them with any other car.

If you drain the coolant then you need to be very careful to bleed air from the system afterwards, as it's a convoluted system. With a bleed valve on the top corner (passenger side) of the Radiator, one for the heater matrix next to the window wiper drive and various ones in the engine bay, all of which need to be done with the expansion bottle suspended above the engine..

...maybe I must change the head gasket...
is it possible to do this without dismount the engine from the car?
It seems very difficult to dismount the heads without to open the chain cover and, to do this, it seems necessary to dismount the engine from the car
please help me

[Alpineandy]

...maybe I must change the head gasket...
Is it possible to do this without dismount the engine from the car?

Yes it is, I know people that have done this, but I haven't had to do it so I cannot give advice.