좀 도와 주세요.

10.길을 잃다.= I'm lost.
~한 적이 있다.= I (have) exprienced something(some situation) in the past.
When I was in Seoul, I (have) got lost.
56. The key is "쓰다가 바꿀 물건이 있는 분" which means " The person who wants to exchange used things.
새 물건을 살 필요가 없는 분 =the person who needs not buy things.

언니, 고마워요.
the person who need() not buy ..

Does (1) 물건을 사고 팝니다 mean 'buy and sell things' ?
And (4) means 'Please come if you have need for necessary items' ?
I'm still not too clear why the ( ) should be filled by (1)?

I think 오십시오 means please come but there's a telephone number so it is not proper.

OMG, I must really pay attention to all the little clues !
No wonder Dong Saeng can guess better than me !