Learning is adding to Long Term Memory
Learning is adding things to your long term memory.
To understand something, you'll have to combine new knowledge. The limit of new knowledge you can combine to understanding the larger concept is 4(+/-1). This is the limit of working memory. It's practically impossible to increase your working memory's capacity.
The only way to learn things that requires more knowledge items is to move things to the long term memory - then you can combine up to 4 items in the short term memory and whatever is in the long term memory to gain new understanding.