YOU SAID:

I was walking my dog through the park when i stepped on a lego

INTO JAPANESE

私はレゴを踏んだときに公園を通って犬を歩いていた

BACK INTO ENGLISH

I was walking the dog through the park when I stepped on Lego

INTO JAPANESE

私がレゴを踏んだとき、私は公園を通って犬を歩いていた

BACK INTO ENGLISH

I was walking the dog through the park when I pressed Lego

INTO JAPANESE

私はレゴを押すと公園を通って犬を歩いていた

BACK INTO ENGLISH

I was walking the dog through the park when I pressed Lego