I had the same sort of thing happen to me when I was starting my first job out of uni. I had manuals and all these references. I would read them on the train and it just didn't click. Then finally after a month or 2 it came together. Just be patient and don't be afraid to ask questions.

That's a difficult place to be. I hope it gets better for you.

That’s not uncommon with something new. You will get better and their frustration will fade. In time this won’t matter. 🙂

I hope tomorrow is a better day at work for you.