If the car is creeping in gear with the pedal down then it's not a cable adjustment issue.
I bet it's difficult to put in ANY gear when stopped. You just notice how hard 1st is because that's the gear you put it into when stopped.
I also bet that you either put it in 1st before stopping or put it in neutral and coast to a stop.
It's either air in clutch line, failed slave *yes bad out of box*, failed clutch master cylinder, failing clutch pedal *not likely*, failing throw out fork * a real possibility* or a failing clutch.