It really depends on your exposure to the language in your environment and your innate ability.
Is studying grammar and attending classes in a language institution harmful if done too early?
Maybe I am being too ambitious setting a goal of six months. In one way it motivates me because I have this pressure to learn a language within a certain time frame but on the other hand if I am nowhere near this goal then I will be disappointed in myself.
Because I have little exposure to natural immersion, I have to do things a little differently to what is ideal. I have to use this time to learn vocabulary. The problem is if I am not exposed to the words I have learned in a book or movie (which puts the word in context), I am going to forget the word. Ideally, I want to read children's books because they are easy to read and I can progress upwards. This is how I learned to read English. I remember my sister teaching me to read with the Disney Golden series, I think the first book was Cinderella, and I recall feeling frustrated because I could hardly read a word. I don't remember what happened after that, but the next thing I knew I was reading all the Disney Golden books we had at home and understanding them.
Then I took out seven books every week from the children's section and read them, starting with the really simple ones and moving onto progressively harder ones. I DID look up a dictionary for words that were unfamiliar to me. I think I did that a lot because I remember the children's dictionary that I used. It was a much-loved dictionary and it had a few black and white drawings.
I really taught myself to read and also taught myself spelling too. My father bought me some spelling books which were helpful because in the school I attended the education was really of bad quality. Because I was taking out seven books a week, I eventually read ALL the books in the children's section. I did this in about a year, two years - I can't remember.
Then I progressed onto the older children section and then onto the adult section (when I was eleven -- I was reading Agatha Christie back then and also dabbling in Emily Bronte which I found very hard at first and then progressively easier).
So reading is the key. I LOVED reading I remember. I became a bookworm.
I wonder if I can do this with Korean. As I said it's hard to find stuff that's easy to read. I don't think reading the WOW is helpful because it has a lot of ban mal in the dialogs. I think prose is easier. I don't know where to find easy prose. I need something that has easy vocabulary.
I think the path is easier if I start off with really easy stuff and work my way upwards. Then I will be a good reader at least if not a good speaker. I can absorb the grammar just by reading rather than listening. Although I will keep up the listening by watching contemporary dramas without subtitles (but I am getting to hate romance dramas with their tortured storylines and characters).
And if I am a good reader I can read Hangeul quickly which makes my progress faster. At the moment, I read Hangeul VERY slowly. I read Romanization much faster than Hangeul. Though I think I am making progress in this area too. Sometimes I intend to write Romanization and I end up writing Hangeul instead before realizing what I am doing.
As I said, the readers have to be very easy. No complex sentences. Just one subject and one verb. That kind of thing. The books I have contain complex sentences. And no ban mal at this stage, I repeat. Ban mal confuses the heck out of me. People say ban mal is easier to learn than other forms but for me this is not the case. I find the informal polite style, the "yo" style, the easiest to recognize and learn, probably because this is the style I learned from the outset. And banmal has different forms and in speaking people switch between the two forms so it all becomes very complicated. My mind can't deal with complexities like that. I like things to be logical and not a mishmash.
Until I get those easy readers I think I will read the WOW comics. When I study vocab and a bit of grammar and then read again, the reading is easier. I can read a bit faster and not be stumped by every second word. If I can get access to the Little Golden Books (Disney) in Korean that would be great. Those books are at my level and don't have too much dialog (and ban mal). Then I can read harder stuff and progress from there. Because I have little exposure to immersion, I have to use this method.
It's a bit embarrassing to admit that you read children's books at my age but it's all for a good cause. The stuff available for adults isn't really suitable for reading. They are mostly dialogs and there is very little prose.
If I learned English that way then it will work for Korean, and remember I had the advantage of being immersed in English when I was learning English whereas with Korean, I am not.