"우리는 그걸 싸워?"
Translation:Do we fight that?
In colloquial language, you can say 그거 for 그것. Also in colloquial language, 를 can be shortened to -ㄹ after a vowel, which gives 그걸 (그거 + - ㄹ).
The Korean sentence is faulty because 싸우다 is not transitive in Korean; I will disable this exercise. We are sorry for the confusion.