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
That didn't even make that much sense in English.