Give up on my current work?

I just turned 17 years old. My older sister asked me to work with her as a retail assistant because the job needs more workers. I just started, and I have to take care of the huge shop alone. Im doing everything, cashier, serving people, checking stocks ect just in one day I'm doing everything already. I'm working from 10am - 10 pm and there's no rest time at all. I'm currently waiting for my N level result.