Applied at Woolworths for Unknown

I recently started my job search as a 16-year-old in Australia, and it's been quite challenging. I've applied to Woolworths twice but faced rejection both times. I also had an interview at McDonald's, which I thought went well. I shared details about my school and hobbies when asked to talk about myself. However, the interviewer seemed disinterested, and after I mentioned my availability in the evenings during school days and mornings and evenings on weekends, I received a rejection about two weeks later. I'm starting to wonder if I'm doing something wrong or if I just need to keep trying. Any advice on how to improve my chances would be appreciated!