I have a ge gss20bdmdww that will not freeze in the frozen compartment and will not cool in the fresh food compartment?

The evaporator might be iced over do to bad fan motor, defrost heater bad,a bad timer motor, compressor not kicking on, low on refrigerant due to a leak, dirty condensing coils. Thes are just things to check. You could try advancing the timer to see if the heater will come on.