For an entire week I had to do a job that I had no idea how to do.
Your employer should have showed/taught you how to do it. I worked in a few part time jobs so far, and my employers always showed/teached me, when I had to do something new. Something that I have not done before. They showed/teached me how and when to do everything, so I always knew when and what to do.
They did train me for the two positions I was occupying so far. The problem was that having sick employees in the middle of the season is quite bad, because you cannot find replacements, so they had to improvise and put me to do their job, even though I didn't know how. They didn't expect me to be perfect, and they were patient enough, but I still had to learn everything on the go. Sucked, but there wasn't much I or they could do about it. Glad to hear you found an employer willing to train you before asking you to do a job. There's a surprising amount of employers who just put you in position, with some on-the-go explanations of what to do, and then expect you to just do the job. I've been there, and it sucks.