May be fired over timing

So I just finished my 3rd week in Aldi. This is my first ever job at 18 and I have been struggling hard to keep up with the times given to me. Getting used to item locations and learning how to stock quickly. The thing is though I’m really behind by a wide margin. My supervisor told me to perfectly card the whole shop in 2 hours by myself and it took me about 2 hours 45 mins. For context this is about 7-8 long aisles my manager and supervisor aren’t happy with me at all and when I rush i sometimes mess up like rotation and get given out too more. Should I just leave and try to get another job in a smaller type of shop or keep working until I get fired or hopefully better.