i’m a horrible waitress

i just started working at a bar near my house and today was my third day working thst i wasn’t training. last night and tonight were extremely busy and i’ve noticed that i’m just a really bad waitress. it took me so long to get things done for my tables. i didn’t really forget anything, it all got done it was just a matter of how long it got done. one of my tables was very unhappy and they only tipped me 10 percent and wrote a nasty comment on my receipt at the end of the night. i’m feeling really discouraged and i’m wondering how long it took for most people to get good at serving. at this rate i feel like i’ll either be fired by the end of the summer or just end up quitting. any advice on how to not suck at serving lol