car in reverse on a hill is having a hard time reversing. what is the cause? on 1991 Chevrolet Corsica

had to press the gas hard for it to slowy reverse uphill. also on a slighty elevated driveway...whats going?

Asked by for the 1991 Chevrolet Corsica
How long has it been since the transmission has been serviced?
I actually bought the car from an older lady Oct 8... So does it look like i need it serviced?
Should have been done a while back. Yes have it serviced, at least a filter service.
k thanks I will get right to it thanks!