"Why are you cutting the fish?"
Translation:Dlaczego kroisz rybę?
Since there are two equivalent variants of the verb "to cut", namely: "kroić" or "krajać" (the latter is a little bit dated though), every conjugative form of the "krajać" should also be accepted. So it is perfectly correct to say:
(ja) kraję (ty) krajesz (ona/ona/ono) kraje (my) krajemy (wy) krajecie (oni/one) krają
PLUS imperative forms kraj (to one person) krajmy (let's cut) krajcie (to two or more persons)
Therefore my translation "Dlaczego krajesz rybę?" is perfectly fine and should be accepted