Hi,
I went to an air conditioning repairman, he checked the gas in the circuit, finally it was the gas that was missing.
He looked for where the leak came from, he detected a valve which is on the circuit (the upper valve on the air conditioning pipe visible in the engine). This valve releases gas.
he changed this valve, he filled me up with air to confirm the leak. after a little shot, it's confirmed, and then he filled up with gas, and the problem is solved.
Thank you all.