fridge is not cooling down and freezer working fine?

There should be a fan behind the panels in the freezer section that turns on and off to blow cold air from the freezer into the fridge. To hear if it is coming on, you can usually open your fridge side, press down the “door switch” manually, and the fridge lights should go and and you would hear the fan come on and blow air into the fridge. Before assuming this is certainly the problem, you would want to unplug the fan and test the two contacts on the plug for continuity (an ohms reading on a voltage meter).

If you find the fan is not turning because it is frozen over, you can thaw out the fridge to melt the ice, but in this case, the fan will work again but now you know your defrost heater is not working.