First interview went horribly but my resume was really good

I'm currently a senior in high school and I've mostly been focusing on school so even with a full comprehensive guide on the questions being asked I didn't really practice much for it. I have a somewhat bad speech impediment so I stutter a lot and can't get my words out that well even talking to people I know I'm comfortable with, how much more if I'm anxious or shy talking to new people. My first interview went horribly. I know for a fact there were some questions I couldn't answer and the questions I could answer I wasn't speaking clearly and I worded everything really badly. On the good side though, my resume was pretty strong for a minimum-wage fast food job and since my mom had connections with the interviewers they said my chance of being hired was over 50%. Since this was my first interview, I would like to know of how I can improve for any future interviews? My parents are pissed rn