frigidaire top refrigerator

my freezer is not freezing and it seems as if the unit is constantly running. the air is cold but not cold enough to freeze food. i’d like to know if anyone has an opinion as to a fix. i do not want to invest money if it would be a waste

If the evaporator coils behind the back panel of the freezer are icing up because of auto defrost failure that will stop the circulation of cold air
check defrost timer, defrost heater, defrost thermostat. In most newer models the timer has been replaced by an electronic control board. If the heater and thermostat are ok it’ll be the control.
Refrigerator Repair Guide: How To Fix a Refrigerator - ACME HOW TO.com