Likely hopefully not your field but I worked 4/5 different temp jobs at manufacturing facilities after turning 18, which while they're not exactly crazy difficult jobs they are physically demanding, frustrating and usually have a pretty steep but short learning curve. In short I was way in over my head everytime I started at another one.

I like asking questions like "How did you know to do that?", "What purpose does this serve?", "Why do we do it like that instead of another way that might seem obvious?" Basically getting people to explain things in a more nuanced way so you can develop an understanding of how everything fits together in the final product. And by extension providing yourself a foundation to put all the stuff that's actually your job on top of. Just don't worry about being annoying, it's their job to make sure you can do your job.

Other than that just keep reminding yourself that all these other people are doing it just fine and they all had to figure it out at some point, so you can too.

Also if you fuck up something stop as soon as you think something might be wrong and go get some assistance. Sure you might be able to fix it or you might make everything way worse, you might be able to hide it or it might come back on you later. It's just not worth the risk to avoid admitting you fucked up. This is kinda generally good advice but definitely applicable at a new job.