Your first photography job is the starting point in your career. This will be like the measurement of your success in the future, so you shouldn’t take it for granted.
First jobs always have this kind of uneasy feeling where you tend to overthink and second-guess. But realistically speaking, you should really give it a go and give your best. Don’t let this chance fly because it’s going to define you as a professional and will be your stepping stone to gaining more clients in the future. You’ll also learn a lot of things along the way.