Starting a new job with anxiety

Sorry if this is the wrong forum
I am 16 and have applied for a new job and basically will probably end up getting it (more of a just ring up and come over sort of thing. No interview or competition)
I have really bad social anxiety and quit my last (and first) job after 4 shifts because of the stress it was causing me. I’ve gotten more confident since than and need to start saving a bit of money before uni. I’m feeling motivated to do it but am also dreading it pretty badly. The place I’ve applied for is out of town and I have no idea where it is. I am terrible at conversing with new people and get flustered really easily and end up embarrassing myself. When talking on the phone I cannot help it but my voice shakes and I can’t think of what to say. I don’t mean to come off as rude but often forget to say thank you and just buckle under pressure. The job would either be working in the kitchen or front of house as a waitress. The kitchen work may be more relaxed but being a waitress may help me gain social skills and confidence with my anxiety. Can I have any advice/ reassurance that I won’t embarrass myself and make a fool of myself.
Also I have bad chronic nail biting as a symptom of my anxiety which may be a problem for hygiene reasons. My nails are incredibly short and messed up. Any advice I would appreciate so much