Im afraid if you turn the freezer off the fridge will go off as well. As this only has one compressor and thermostat on it so when you turn it off the whole appliance will go off.
What you might best doing it turn the appliance off and keep the fridge door closed as that will keep it air tight and it will stay cold.
Then empty the freezer and put a few towels do.
Then put a bowl of boiling water on each shelf inside and this will help it defrost faster.
You can also use a hairdryer. Hopefully that will take an hour at the most then you can turn the appliance on and the fridge will still keep its cold in there.
Hope this helps. If you need anymore info just get back to me.