If the fridge section isnt getting cold as it should then its more then likely too much ice on the fridge evaporator and fan stopping the air flow.
What you can try before getting someone in is a full defrost. Turn the appliance off for 24 hours and leave the fridge door open. This will allow the ice in there to melt away.
After 24 hours turn it back on and fingers crossed this sorts the fault from there.
But if you find in say 3 weeks time it does the same again then theres a fault on the auto defrost side so you need to either check the defrost heater and defrost sensors out and see if faulty or get an engineer in.
But fingers crossed the defrost sorts it.
Im afraid so as its one unit so if the fridge goes off the freezer will as well.
Unless you are handy at diy repairs and in this case empty the fridge and turn it off.
Then you need to remove the plastic back panel in the bottom half of the fridge.
Behind there you will see the evaporator. Melt all the ice on there with a hair dryer and also make sure all the ice is clear from the fan as well.
Then see how it goes from there. But it is a bit of a strip down doing it that way.
No worries. If you need anymore info just get back to me.
If you could also remember to rate the answer that would be great.