how can i not get stressed out at my new job?

how can i not get stressed out at my new work?

i (21m) started working as a temp sales assistant in pandora. my coworkers keep telling i’m stressed out. it has been stressful, even though i am part time, because this is my 2nd ever job and i’ve never worked in sales before and first time working with alot of people.

i’m usually quite calm but there’s alot to take in, alot to learn about specifics and such. theres one colleague who seems unimpressed with what i do. i make a mistake and she says to me “didn’t you learn this already?” “you should’ve learned this in training” (i only had 2 days trainin) “i already showed you this”. but i don’t want to blame her but its such a mood killer for me because it’s basically a backhanded compliment. i always find myself rushing to impress not just my colleagues, but mainly myself. it’s just how i’ve always been. i set such high standards for myself that i expect myself to have everything to a t as soon as possible and get pissed off when i mess up or i don’t know a certain thing. a perfectionist. after every shift i’ve had i go home stressed out and kick myself cause i messed up and how i didnt know this or how i should’ve handled that.

i’m jealous at how my coworkers can just talk to customers with knowledge and natural. i also hate how they just come and take over from what i’m doing and just sell better than i do. it genuinely hurts me and my ego and pisses me off how they can just do it and i cant, even though i dont know much of the products. i want to just do my own thing but i need constant assistance for product knowledge. now that we’re getting to christmas time i need to learn things as quickly as possible.

i just need some advice. how can i learn things quickly? how can i stay calm and not rush? they all say i’m a nervous reck. literally any advice on my situation.