If you hit the barrier of knowledge taking, just do two things - start rereading everything in a mechanical way, even though you may not have the feeling to understand, it diffuses slowly into your brain, if you are through all matrial start all over again - usually the last one gets it after 5 passes or so - second, do the documented questions over and over again the same way. There are some things you can not mentally burn into your knowledge, but they have to be based on experience, meaning in aviation there are things you have to do the old boring way of repeating many many times (as was a usual way to "learn" in the old days know by our ancestors - in contrast to nowadays "you only have to explain it in a lengthy way, because everybody can do everything if she/he is only allowed to do so ... no, this is proved to be wrong for aviation skills).