Freezer works fine, refrigerator loses the ability to cool until barely cooling at all.

My ref runs smoothly at first but until it reaches -9 centigrade with compressor running with refrigerant flowing thru the tube, then it slowly loses its cooling ability but with compressor still running. the compressor continues to run for 10-20 minutes but with rising temp( i have a thermometer inside the freezer), the defrost timer kicks in for 5 minutes, then the power shuts off. After another 5 minutes, the compressors kicks in again, full power, and complete the cycle again. the temp goes to -7 to -9 C. The problem is, I can't get/make ice from my freezer even if i adjust the defrost timer from minimum to maximum

First thing I would do is remove the back or bottom to expose the evaporator coils. If the coils are all iced over you do have a defrost prolem. You ill need to locate the defrost timer and most times there in the fresh food section. Where on your model I cant tell you but it will have a slot for a flat head screw driver to turn the shaft. Turn it untill you hear a click. That will put the timer into defrost.Then check and see if the heater is working. if not you need to check the heater and the defrost terminator, The trminator is a small round disk with 2 wires on it. you will need to ohm it out to make sure its not stuck open. If it is thats your problem. If not ohm the heater. if thats good replace the timer.And are you sure the evaporator fan is also working? If it is not you will not cool the fresh fod section.There should also be a schematic maybe on the back of the unit or on a tech sheet in the back or behind the kick plate. Good luck