Jeongmin S. answered 10/31/20
Easy to learn Korean L-S-R-W all at once with a native Korean speaker
You are curious about the difference between '힘들다' and '어렵다' and the use of sentences.
The '힘' of '힘들다' mean is physical, emotional and mental meanings such as power, feeling and energy.
'들다' is an abbreviated expression that means '들어가다 put into' as the form of the ending of a word.
Therefore, '힘들다' can be seen as a meaning of '힘이 들어가다', which is a physical, emotional and mental effort.
'어렵다' can be seen as a judgment of physical, emotional and mental abilities depending on the situation.
Therefore, if '어렵다' represents the primary state of the problem situation, it can be regarded as '힘들다' as an additional secondary state to that situation.
However, since the steps that ordinary people perceive when judging a situation are momentary. They do not consider the first and second steps largely.
Since these two expressions have similar meanings, they can be used interchangeably depending on the situation, or they can be used together in one sentence because there is a difference in order as I said.
In summary, both are ways of expressing a situation of physically, emotionally or mentally. The '힘들다' is mainly used as a concept of power to enter a problem situation, and the '어렵다' is used as a concept of a measure of the ability to judge a problem situation. The two words have similar meanings and can be substituted or used together depending on the situation.
Therefore, it is necessary to learn appropriate expressions through various examples.
EX -
1) 이 가방은 너무 무거워서 오래 메고 있기 힘들다.
This bag is too heavy to hold on for long.
2) 이 슬픔을 견디어내기 힘들다. / 이 슬픔을 감당하기 어렵다.
It is difficult to bear this grief. / It is difficult to handle this sadness.
3) 그런 복잡한 상황은 바로 해결하기가 어렵다(/힘들다).
Such complex situations are difficult to solve immediately.
4) 시계를 정교하게 조립하는것은 나에게 어려운 일이다(/힘든 일이다).
Precisely assembling a clock is difficult(/hard work) for me.
5) 너를 오래 기다려주기는 어려워(/힘들어).
It's hard to wait for you long.
6) 나에게 이 수학문제는 어렵다. 그래서 풀기 힘들다.
(나에게 이 수학문제는 어려워서 풀기 힘들다.)
For me, this math problem is difficult. So it is hard to solve.
7) 나는 어른을 어려워한다. 그래서 어른들과 함께 있는게 힘들다.
(나는 어른을 어려워해서 어른들과 함께 있는게 힘들다.)
I have difficulty with adults. So it is hard(uncomfortable, burden) to be with adults.
8) 어려움에 처한 친구를 도와주지 못 해 내 마음도 힘들다(/아프다, 슬프다).
My heart is also hard(torn, sad) because I can't help my friend in need.