Hi,
What is the model number of the refrigerator?
Condensation means that the fridge walls are colder than the surrounding air and the moisture in the air is condensing to liquid form.
Refrigerators are designed to keep the cold in as best they can and not lose it to the outside.
Seeing the condensation on the back wall, presumably behind the freezer compartment may (stress may only) indicate that there is an ice buildup there behind the panel at the back of the freezer compartment. Hopefully it is not an insulation/sealed system piping problem
Normally there should be no ice build up as the auto defrost action should melt the ice every 8-11 hours. Also having ice there wouldn’t make the freezer any colder but if the ice is in close contact with the inside wall the cold may eventually penetrate through the insulation between the inner lining and the outside cabinet wall.
The panel, inside at the back of the freezer compartment should come out so that you can check what it looks like. Be aware that an evaporator unit may be there and that it will be icy cold so don’t touch it with your bare hands as you may literally stick to it. Also it is always safer to disconnect the power to the refrigerator when working on it
With regards to the fridge door, I don’t know but it also must be cold to get the condensation forming. Conjecture on my part but if cold air was escaping through the door seals it might make for a colder door on the outside but maybe not. Place a piece of paper between the door and the door jamb and with the door closed try to pull it out. It will come out with a bit of effort, but it shouldn’t come out that easily and definitely not just fall out. Try this at various places around the door, top, bottom and both sides. Given the age of the fridge the seals should be okay but it is a simple check and it doesn’t take long to do ;-)