Not cooling properly

That is a defrost issue you need to remove the rear panel in the freezer section. If the evaporator is built up with excessive frost you need to defrost the frost build up with a hairdryer or steamer. Then you need to check the heater for continuity and the defrost thermostat for continuity as well, that is clipped to the evaporator. It has to be cold to test it and it should read continuity with an ohm meter as well when cold. If all that tests good you likely have a bad defrost control.