I was 13 (assuming this is your age since you're asking) when I got my first "job" as staff. It was a lot of responsibility, but it was also on a pretty small server (a max of 40 people on most times). I think if this is the first time you want to be staff on a server, that you may be biting off more than you can chew if you don't familiarize yourself with the responsibilities and situations that come with being a staff member.
However, that doesn't have anything to do with you as a person necessarily, you seem very nice and helpful! Just know that the larger the server, the more demanding the job is.
Maturity is a big thing too, which depends person to person. If you have someone behaving super inappropriately or being rude to you, they want to know that you can handle it the right way without letting it affect you personally, or retaliating (there are other things too, but this always comes to the forefront in my mind). I think the only reason I was picked to be staff at such a young age was because the senior staff members hadn't realized I was so young until I applied. the things trauma can do to a kid, amirite? yikes lol