YOU SAID:

if you eat food, i don't eat mashed potato

INTO JAPANESE

食べ物を食べるならマッシュポテトは食べない

BACK INTO ENGLISH

If you eat food, don't eat mashed potatoes

INTO JAPANESE

あなたが食べ物を食べるなら、マッシュポテトを食べないでください

BACK INTO ENGLISH

If you eat food, don't eat mashed potatoes