u/Inevitable-Movie-309

So I am currently 15 and turning 16 in just a few days and was going to ask my boss to change my contract as I always work Tue, Fri, Sat and Sun for 3 hour shifts, however I found out one of my friends who work at another nearby store is already working 16 hour shifts and they are not set days and hours like mine, so when I'm talking to my boss about the contract change what should I say to change it into that? Sorry for the potential confusion, a bit hard to say what I want to say. 😂