Hi @zion86944
I'm having problems sourcing information regarding the refrigerator but check if you can hear a fan running inside the freezer compartment when the compressor motor is running.
With most refrigerators that have only one evaporator unit, there's a fan inside the freezer compartment located near the evaporator unit (behind a panel at the back of the compartment - access it through the door at the front of the refrigerator - i.e. remove the panel) and it blows air across the freezing evap unit and into the refrigerator compartment to cool it down to the desired temperature.
The freezer is cold because that's where the evap unit is located.
The fan should stop when a door is opened (either door) and start again when the door is closed. The fan will run as long as the compressor is running as well.
If you can't hear the fan at all then there may be a problem with the fan, the power supply to the fan, the control board or it could be that the fan is completely iced up due to a defrost problem.
With auto defrost refrigerators (I don't know if yours is because I can't find any info on it) the compressor motor is stopped every 8-10 hours and the defrost heater under the evap unit is turned on to melt any accumulated ice off the unit to drain away.
The defrost cycle lasts for about 20-25 minutes after which the compressor is turned on again
If the fan is iced over then it could be due to a faulty defrost heater, defrost thermostat, defrost timer (or control board) or a blocked drain.
You may have more luck if you search for Hisense R-Z270AUK7K parts than I did. At least if you find any suppliers they might have a list of what parts are available if you do find out what's wrong.
Sorry that I can't be of more help.