memorising comes with practice, but to be honest the curriculum is there to familiarise with the language, if you need to use something and don’t remember how, google it - no shame, everyone does that (the best programmers are black belts in google-fu! and reading documentation also)
there are a few websites that have the documentation for the languages, it will be both what comes up the most in google research and maybe also those you will start bookmarking
I used to take notes, but I found I never read them. I’d rather repeat something a few times instead of trying to write it down out of its actual use-case.
1 time to get the idea of what it is, then apply it as often as possible. I never try to memorize anything. I’d rather use something multiple times, either with the help if looking it up, reviewing code I already wrote with it, or by re-learning it on the spot (using some references like mdn usually help)
Lessons are there to show you what you can do, but they don’t make you learn. You need to take what you find in the lessons and apply it a few times to “learn” it. I’d compare it to reading about how to ride a bike and just expecting to be a pro once you get on one. You need to get on the bike and ride around a while to get the feel and to teach your brain how to handle it.
FCC’s core concept is to present you tools via the challenges, but you actual learn them during the projects, which will require you to struggle and play around with the problem and solutions in a real-life type environment. Don’t try to memorize everything upfront and expect to know the concepts, it doesn’t work that way. If you find yourself not understanding, you need to go back and repeat the challenges to refresh your memory and maybe see solutions to problems you find when you go out on your own.