Arif Pasta

Hi, Am based in Kenya and have an Audi A4 sport 2001. Its Air conditioning had a problem but having fixed that, it developed over heating problem. Temp gauge stopped work and it over heats while running on idealing. I have changed the thermostate, 2 temp sensor one at the bottom of radiator, water pump but still the problem remains. Also the fan doesnt automatically ran when temp goes up. I feel also water not circulatig in the system. Hope someone can assist resolving this issue. Thanks