I’m all in knots over this affair
(난 이일 때문에 답답해 죽겠어.)
This statement is implying that a person is tired and fed up with the current situation.  When a situation occurs that is overwhelming and a lot to handle, a person can say that ‘they’re in knots over this affair.’

Why do I get sick to the stomach? 
(왜 속이 느글거리지?)
This is a person asking why people get stomachaches.  People will get stomachaches if they eat the wrong kinds of food or if they have bad cramps.

Food isn’t settling well
(먹은 음식이 소화가 잘 안돼.)
This is implying that the food you ate is upsetting your stomach. Sometimes this happens when you eat too fast or eat something that is foreign and your stomach is not used to.

My stomach is upset
(배 아프다.)
These statements are saying that a person has an upset stomach. You would usually say this statement if something is weird or hurting in your stomach.

I got a relief after I took something for indigestion
(소화제를 먹고 속이 풀렸어)
This is stating that a person feels a lot better after taking medication for his stomachache.  When a person has a stomachache, they would usually take medication to relieve them of the indigestion.

I finally had a breakthrough in English
(난 드디어 영어 달인이 됐어.)
This is stating that a person finally broke the English barrier and is able to speak English fluently.  By having a breakthrough, you are implying that you have achieved or developed a technique that broke the barrier that was holding you back.

What’s the most effective way to gain full command of the English language?
What’s the most effective way to attain mastery of the English language?
(영어를 통달하는데 어떤 방법이 가장 효과적인가요?)
This is asking if there is a certain method or technique that works best to break the English barrier. 

I think the most effective way to instill a sense of inflections is by studying inflection-oriented materials, such as dialogues from films and T.V.
(내 생각에는 영어 억양을 익히는데 가장 효과적인 방법은 영화나 TV를 보는 것이다.)
This is implying that the best method to break the English barrier is to study dialogues from films and television. By studying these materials, you can learn how to speak the language and start to understand what they are saying.