AC not cooling down well

I have a felicia 1.3 97. I live in Dr where is very hot the whole year long. I took my car to the technitian to check on the air conditioner. He checked the system and end up completing the refrigerant gas. The problem is when it is very hot outside it does not cool down well, but if it is raining or it is in the evening time it works a bit better. I noticed that it taking in the air from outside (bonnet)and not recirculating the air. The recirculation button is stock in. What should I do? Please advice

Note: I read the skoda manual, so i can deal the AC more efectively.