They should really put a small fan that uses less power so this doesn't happen

My car is still not fixed. I am having issues with the car over heating. When I am driving I am fine but as soon as I stop at a stop sign the temperature climbs and my air conditioner turns off. I have already taken it to a mechanic and he replaced the thermostat and we added water and still the problem is going on. The mechanic also bleed the line to see if there was air in the lines. I don't know what else to do. I need help.