Beko poor cooling

Hi fridge freezer beko cxfg1685 wery poor cooling try to check components freezer temp. sensor resistance down when temp. going up heater resistance also look ok, 4wire sensor or thermostat short when cold and resistance going up when temp. going up and fridge temp.sensor resistance up when temp down but no access to sensor for testing, heat. After switch off for few minutes start work ok and after some time finish cooling and just fan running. Please help what else I can check or what readings expect.