It's normal for the outer walls of the freezer to get warm or hot when the compressor is running; refrigerant lines inside the cabinet walls remove heat from the compressed refrigerant. The hot refrigerant helps control cabinet humidity to prevent the cabinet from sweating.
If the walls get extremely hot, the condenser fan could be malfunctioning. The condenser fan blows air across the condenser coils to help cool the compressed refrigerant before it enters the evaporator. Replace the condenser fan if it doesn't run when activated.
Dirty condenser coils can also cause the hot freezer walls. Dust build-up on condenser coils interferes with heat transfer so the refrigerant stays hotter as it leaves the condenser and travels through lines in the freezer walls.
Performing routine maintenance on the freezer can also help keep the freezer walls from getting hot. Cleaning dust from the bottom front grill can improve airflow across the condenser so the refrigerant is cooler as it goes through lines in the freezer walls. Cleaning the door or lid gasket can prevent air from leaking into the freezer compartment, causing the compressor to run longer and heating up the refrigerant travelling through lines in the freezer wall.