The fridge section on these models is just an insulated box with all the coldness coming from the freezer section via a fan.
Check the top of the freezer section and look in through the grills at the front. Can you see it all iced over ? If the answer is yes , then a quick fix is to switch the whole appliance off for 48hrs. Be aware that if you go down this route , there will be a lot of water coming out the front AND also filling the clear container above the compressor at the rear of the machine. After a complete defrost , your fridge and freezer should both start working ok.
Now , how old is the appliance and have you had any modifications done to it ? There is an fault relating to the defrosting side of the freezer evaporator but this normally occurs within the first 18 months of use. If your appliance is less than 2 yrs old , the repair should be carried out free of charge by BSH ( Bosch Siemens ) . If its older than 2 yrs , then you might have to appeal to their ‘benevolent side’ for a solution.