Wow, big topic to answer... 1. ~ㄴ 김에 : when, while, the same time... = 가는 김에, ~하는 김에 possible to change to '~하는 길에' (on the way doing something) 2. ~ㄴ 데다 : if you know "게다가", it's similar to it. (Verb + moreover) = 다리를 다친 데다가 머리도 아프다. 비가 오는 데다가 바람도 분다. 3. ~ㄴ 반면에 : 반면 is 'the opposite side'. So, 반면에 can be 'However, while, on the other hand' = 나는 공부에 집중하는 반면에 채팅도 하고 있었다. 4. ~은/는/이/가 indicate the noun's part of speech, 'subject'. So, it is the basic part of constructing sentences in Korean. =오늘'은', 나'는', 사람'이', 우리'가' * A letter can have two parts or three parts. You can study '받침' to figure out which one to use among the four. 5. 셈이다 is similar to 'kind of , like, as'. =우리는 게임에서 비긴 셈이다. 내가 일을 다 한 셈이다. 6. ~ㄹ까봐서 can be used to indicate that the speaker is worried about the listener. =엄마가 걱정할까봐 전화했어요. I called you to make sure you are not worried about me. 7. ~ㄹ 지도 모른다 is also showing that the speaker is worried or not sure of something. = 그녀가 기다릴 지도 몰라. She might be waiting for me now. *Sorry about not being thorough. Just rough explanation I gave..TT Good luck.