Yeah I get that, I ignore a lot of what I don't catch the 1st time, then try and pick bits off at a time and find out. The 1st read was like, get the popcorn, 2nd time I sat with Google for hours trying to make sense of things, lots and lots on you tube and Instagram too if you're more a visual/hands on learner.
3 weeks in a classroom does nothing for some, who can then pick a job up in a day shadowing someone who knows it.
Others can know the lot on paper and then couldn't complete a task practically if they're life depended on it.