What you can do is compile your own vocabulary lists. Read a book you are interested in or watch a drama you are interested in and make lists. You don't have to do the memorization while you are making the lists. You are just watching or reading in a relaxed fashion and making lists. Once you have made a list for the chapter or for the episode (if it's a movie), then sit down and commit the words to memory. Try and get the right form of the word, that is, note whether it is a noun, verb etc. Then after memorizing the words, read the same episode again or read the same chapter again and see how much you comprehend. I think you can easily learn about 150 words a day if you are studying full time. In about 100 days or less (3 months) you will have learned about 10,000 words. If you study furiously like some of those people on YouTube do, you can learn about 200 words a day, maybe 300 words a day. Then you will learn all the words you need in 30 days (9000 words). So you could have done a month's worth of intensive vocabulary study. Either buy vocab books that have exercises for practising recall. Or you could make your own lists by watching or reading something. You would have to study intensively though. The selecting your own words is a more time-consuming method than the one where you learn from vocab books, but the first method has the advantage of context.
So you can really learn to read and understand grammar (basic) in about six weeks (1.5 months) - 2 weeks to learn grammar (and listen to mp 3 files) and 4 weeks to learn 9000 words. So you can have a pretty good handle on a language in about 6 weeks really. You will be able to read a newspaper and story books and understand quite well what's going in a drama. You can catch the gist of what the news is about when watching TV. You will be able to follow a person's conversation if not be able to participate.
You might not be able to read manwha though - manwha contains heaps of colloquial speech.
You probably won't be able to converse well.
But then after the 1.5 months, you can do INTENSIVE immersion with interacting with Korean speakers (5 hours a day) and learn Korean conversation in about 4 weeks of this.
So it IS possible to learn a language in about 2.5 months but it would require marathon sessions of study every day, just studying Korean and doing nothing else.
It would also help if you had a genius brain because you would only have to see a word once with its definition and you would remember its meaning always. A genius would probably have photographic aural memory. They would be able to hear a sentence once and can repeat it exactly without a mistake and with the correct intonation and everything. If they knew the meaning of the sentence, the genius would be able to use the sentence themselves in future. And this is just after ONE exposure.
Geniuses have an easy time I have to say. Even if they learn using the didactic method, they can still become fluent. They don't need that much exposure to the communicative method to pick up the speaking and grammar.
Needless to say, I wish I was a genius!
But I think some intelligent people also learn languages well and have good pronunciation - if they are determined to learn that language and are persistent. Then these intelligent people become super-good at the language and sound almost like native speakers. This is when they are highly motivated to learn that language and it becomes a hobby for them. Then there is no stopping them. They also become very good at reading and writing. They are usually good in all four areas. They don't make common mistakes in speech that the average learner does - eg. dropping the 's' in plural words or not saying the third person singular correctly. They also don't mix up 'she' or 'he'. These intelligent people are very detail-conscious. I have come across some very intelligent people who are very good at English even though they never spent a day in an English-speaking country or didn't spend any time in an English hagwon.
