Korean in the app version
Korean is hard in the app without explanations. Deducing why the verbs are the way they are and all the word endings. Can't wait for the web version. Is spoken korean different that written?
For the most part, spoken and written Korean are exactly the same. Of course, you'll want to judge the formality of the situation you're in when choosing which verb endings and words to use. For instance, in any formal situation, written or spoken, you'll want to use the -ㅂ니다 style.
저는 한국어를 공부합니다
But, the same sentence, when speaking or writing to a close friend who you use informal language with, you could effectively say:
나 한국어 공부해
They both mean "I study Korean"
In the formal situation, you may choose to use the polite version of "I/me," which is 저 instead of 나. And you should probably be as grammatically clear as possible, hence the specific use of the -는/은 and -를/을 particles.
In the informal situation, you simply chose to drop the particles and use the informal words and endings, because it effectively has the same meaning. That's not to say you should drop particles to sound informal, but for simple sentences, this would be the case.
Here's a couple more examples of some formal and informal situations in which the meaning is identical, and you can use both in speech and writing:
~저에게 당신이 방금 쓴 편지를 주세요
~나한테 너 방금 쓴 편지 줘
~Give me the letter that you wrote a minute ago.
~여기서 공원에 가고싶으면 티머니카드를 사고 지하철 타주십시오
~여기서 공원에 가고싶으면 티머니카드 사고 지하철 타
~If you want to go to the park from here, buy a T-money card and ride the train.
~네, 저는 지금 근무하는 중이라고 했습니다
~어, 난 지금 근무하라고
~Yes, I said I'm working right now.
(This one is a little less literal of the same thing. The first sentence is literally "Yes, I said that I'm in the middle of working now" and the second sentence is literally "Yeah, I said I work now", but both can be translated less literally as the same thing.)