GE monogram fridge. not cooling enough right side. Icing up a little in the freezer

Hi everyone! I have an about 18 years old GE monogram fridge which is not getting enough cold in the fridge section ( right one ). I checked the air, coming from the freezer ( on the top left corner in the fridge side). Found that it blows very slow. But when I opened up the left freezer door a little, it started giving me much stronger air pressure. The problem is - I couldn`t found the return - it seems to be just one air way - kinda in to the fridge ( behind the dumper on top of the fridge side. It is obviously not a super common design but like I said - the fridge is about 20 years old. Where should I clean the air duct with steamer? Inside the freezer I think but I do not know exactly.

http://fixappliacetoday.com