In your posts it sounds like you had a total of 2 1/2 hours of training on a cashier job. The next day there was a teen that wanted you to work faster at that job.
Sounds like a cashier job at a high volume fast food place.
The duties might seem simple but can be demanding. I think this description explains what I mean.
Fast Food Cashiers are personable employees who collect payments from customers in a fast paced working environment. Typical resume samples for Fast Food Cashiers highlight tasks such as greeting customers, taking and delivering orders, assisting with food preparation, solving customer complaints, handling monetary transactions, and keeping the restaurant front area clean and well-stocked. The ideal candidate has excellent numeracy skills, is enthusiastic and self-motivated, and communicates effectively with all sorts of people. Education requirements are minimal, and most Fast Food Cashiers resumes mention a high school diploma.
I sympathize with you if that is the situation you are in. Complaining not likely to do you any good. You do have a choice. Quit or do the best you can and see how long you last.