"Fighting is good."
Translation:싸우는 것은 좋습니다.
것이 is 것 + subject particle 이.
게 is 것이 but in speech (it's faster).
Same with 것을 (것 + object particle 을), abbreviated as 걸; and 것은 (것 + topic particle 은), which is abbreviated as 건.
Try to read it slowly since it can get confusing, it also took me a while to get. I hope it helps.