When you have a cold freezer warm fridge situation it could be many, many things.

However there are 2 that are by far the most common.

1st Maybe a defrost problem… Snow on the walls is a sign of a problem with the auto defrost system. This would make your freezer compartment unable to shed the snow which would then insulate/block the evaporator coils from the air in the fridge/freezer compartments. Check for frost/snow on the back wall or floor of the freezer compartment. If your freezer has snow on the back wall (or in some freezer on top models bottom floor) then that is a sign that you may have frosted coils. Melting that frost until the coils are down to bare metal again would temporarily restore the function of your fridge/freezer. If you feel up to the task you can empty the freezer and melt the snow by leaving the power off or unplugged for 24 hrs. Just remember that when that snow melts it often makes litres of water come out from underneath/behind so be ready to catch it and clean it up. Keep in mind the auto defrost system would still need repairs otherwise the snow will build up again. A fridge which is unable to get cold enough will run almost all day. This puts wear on the expensive sealed system compressor (the heart of the fridge). It is important to prevent wear on the compressor.

2nd common problem is broken/blocked fan. This is sometimes forewarned by some loud noises. To see if that is the problem listen for fan sounds. Open doors too see if its in the fridge or freezer compartment. *Note that some models turn the fan off when you open the door. With those models you need to spot the door switch/button which gets pushed by the door when its in the right position. Push it in so it thinks the door is closed.

If your fan is not working it could be blocked by something like food or ice. It may be a burned out motor, a broken fan blade or lack of power supply to the fan. You may need a repair person to solve this problem.

If your fan is working check the vents for air flow. Sometimes snow/ice/food may block the vents. If you can unblock the vents you may restore the function of the fridge. If not, you may need a repair person.

There are also fans underneath many modern fridges. If they stop working it would make it unable to shed heat from the condenser coils. This would make the fridge very inefficient. Constant running may harm the compressor.