i never stopped 〔thinking / to think〕 about the benefits of 〔have / having〕 a clean room.

여기서 왜 to think 인지 모르겠어요

but dolphins don’t limit 〔themselves / them〕 to 〔imitate / imitating〕 each other.

여기서는 두번째 imitating/imitate 이거요

because the same kind of accident 〔was occurred / occurred〕 again, we were quite prepared to see it.

이것두요..ㅠㅠ 그리고
while this simple game will not solve every your problems, if you can give you an enormous amount of needed perspectives.
여기서 밑줄친 every는 맞는건가요? 에브리 뒤에는 단수 명사가 와야하는데 틀린거 아닌가요그리고 집합명사/군집명사가 복수로 쓰일때와 단수로 쓰일때의 차이점을 알려주세요 ㅠㅠ
도와주세요 감사합니다