beko fridge freezer too cold

It sounds like your fridge might need a new tstat, or the damper between fridge and freezer is stuck open, instead of regulating the amount of cold air that enters the fridge section. I'm not familiar with the layout of this particular fridge, as you need to post model number of the unit, but try finding where the cold air enters from the freezer section, and removing panels to access the damper. Try moving the damper yourself by hand. Carefully. Don't bend or break anything doing it.