YOU SAID:

When i was walking i saw a dog

INTO JAPANESE

歩いていたら犬を見ました

BACK INTO ENGLISH

I saw a dog while walking

INTO JAPANESE

散歩中に犬を見ました

BACK INTO ENGLISH

saw a dog while walking

INTO JAPANESE

散歩中に犬を見た

BACK INTO ENGLISH

saw a dog on a walk

INTO JAPANESE

散歩中に犬を見た

BACK INTO ENGLISH

saw a dog on a walk