Not cooling nor freezing

I have a Samsung fridge RFG297AARS twin cooling which is about at least, 6 yrs old. My situation is that the freezer had stopped working one night completely. It had showed me an error code of 04. After replacing the defrost fan and temperature sensor. It still didn’t freeze right. Now the upper lever isn’t cooling now. The temperatures on both are Freezer 72 / Fridge 54 degrees. The compressor is warm to the touch and vibrates, which I’ve heard is a good sign. The fan towards the compressor is working fine. The coils are clean. What could be the initial problem here now? I’m at wits end and don’t feel like spending more cash on the fridge. Can someone give another advice as to what “could” be the main problem? I haven’t checked for coolant level since i don’t have the proper tools for it. Thanks in advance.