Learning quickly usually means you "care" more (in some way are more motivated, curious, or passionate than others), work harder, work smarter per your time, or spend more time thinking / working through things throughout your day. Honestly though, people do have a "knack" for learning certain things in certain ways. I will also go so far as to say there's a "knack" for memorizing vs. computing thought. By all means you can be born good at both or get good at both, but usually you have a personality and tendency to like/dislike one or the other and it will force your thinking patterns to be "better" at one naturally. There are visual-, tactile-, audio- types of people and others. You can get better at each one, but there are some that you will be better at without as much effort as the others.
It can make you incredibly unhappy to spend all your thought/time doing things you don't want to or doing things you like the wrong way. Don't do it. Life is too short. You might think you are terrible at something, but be going about it the wrong way. For example, I am a visual learner. I learn very well and very fast writing, reading, drawing concept maps, reviewing, testing myself, and reviewing more all visually. You would think I was terrible at something if you made me try and do all of it by listening to audio only (as many times as I wanted) and being able to only talk to people with no writing allowed. I'm the same person, learning the same topics, but some methods make things stick better.
Sometimes you have the leisure and time to improve at a learning skill. If you are mostly visual and keep working at audio, you will be able to become better at both! However, if you're pressed for time and performance (say.. medical student) you are probably better off figuring out how you learn and overusing that to death so you get some time to sleep. Learning is about learning yourself and what makes you understand the best (in a good amount of time with a worthwhile retention).
Other factors in learning are awakeness (did you sleep enough?), happiness with life, overall health (diet / exercise help), background knowledge (in the same, or other seemingly unrelated things), self-confidence, openness (are you fighting learning it? do you hate your class or teacher?), and good habits (do you habitually distract yourself or did you form good habits at sitting and focusing over the years?). Background knowledge in learning, critical thinking, or being familiar with a topic helps a lot.
I've seen people waste unimaginable amounts of time on other thoughts and it cuts into their learning time. Many of them never realized the problem and became frustrated. For example here are a few (look out for these, see if any sound like you..):
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Thinking about things happening in the day.
Thinking about how every last little thing works.. then getting hung up on it.
Thinking about how boring things are.
Thinking about how much they hate what they are doing.
Thinking about how something is named in a dumb way.
Thinking/worrying about what someone else thought of them that day.
Thinking/worrying about failure.
Thinking about how to get through and just scrape past some class / school / graduation date.
Thinking about what they will do in the future (which to some extent is productive, as it can be planning and motivating for the current task).
Thinking about whether they will get a call / text / message / whatever.
Thinking about how to display some status update on social media.
Thinking about said random noise / shuffling / movement in room.
Thinking about how many pages they read or how far they are getting in the book.. without actually reading the book.
How to fix some of the above things.. make sure after every page (or paragraph / sentence) you actually comprehended, can summarize, and remember what was written. If you don't remember things you read, record yourself speaking the page and listen to it. If you hate audio, either get Dragon or transcribe audio yourself. If you don't map memory to typing, then write it out, or vice versa. Repetition and quizzing yourself helps. Believe in yourself and don't worry about other people. Also don't get hung up on something too long, one nitty gritty detail won't kill you and obsessing over it gets emotional and wastes time. Sometimes its better to write it down, address it later when you know more, or go out into the world and ask someone online/in person to share some of their knowledge with you. Don't worry about "telling" other people on social media or real life how many chapters you read so you sound good. No one cares how much you read if you didn't learn. Learn for YOU.
You are made up of your years. Your years are made up of your months. Your months of days. Your days of hours. And your hours of minutes and seconds.. how you spend them with your actions and thoughts. If you waste your thoughts on garbage (listed above), it will take you a very long time to get through things when you learn them. I don't advocate not addressing these things, they are important but in their own time. If your job is to be a student and to study, or you made yourself a goal to learn something.. then make sure your time is spend smartly working on the task at hand, in the present. Having a plan in mind, an approximate flexible schedule (don't be too hard on yourself if you don't make it, count the positives and don't let things hold you back!), and a goal help immensely.
I've been told I am a fast learner. Sure? I'm smart but no genius child. I am a very hard worker, extremely goal oriented, and very good at focusing at the task at hand. I hate garbage thoughts (negative feelings, negative things from other people, not believing, worry, unnecessary life drama, emotional or irrational reactions). I don't have any form of social media.. the most I have is this blog for software, one for food (my hobby is cooking), and LinkedIn.. I feel most other social media provides more unnecessary distraction than good, but it's just my opinion (however, there are times where it will HELP your career a lot if you are a public speaker, actor/actress, athlete, traveler/have friends at a distance, etc..). I try my best not to worry about others or let them take time away from my thoughts. Of course, I'm human and do care very much what a few people close to me think, but other than that I don't waste time on drama/life garbage. I can blatantly ignore my surroundings, to the point of likely unhealthy if some event were to occur behind me. I can be called "spacey".. I'm there, but I'm not. If you leave me alone a couple minutes I'll have started thinking or planning out something else in my head I was working on before.. for example working through a puzzle, rehashing as many words I can think of from a language I'm learning, finding another way to approach something, or walking through a concept map of something I've learned. Your idle time is A LOT of your day. Your time spent walking, exercising, traveling, driving, sitting, etc.. and if you took all that time, you can get very good at what you already do "quickly" relative to someone else who is thinking about their Facebook post.
You don't have to do this with your time, only do it if you want to.. do what makes you happy. If you enjoy social media, art, history, science.. anything then spend your time on it! This post if for if you are trying to learn and not sure why you may not be getting the results you want. Not everyone wants to learn a ton of stuff. For some, life is a comfortable place and relaxing is important. For others success and moving up. But, for me.. I like to learn. I'm good at learning and it makes me happy so just sharing some mistakes and advice if you too enjoy learning.