YOU SAID:
yesterday i ate a potato and ate a potato
INTO JAPANESE
昨日じゃがいもを食べてじゃがいもを食べました
BACK INTO ENGLISH
I ate potatoes yesterday and ate potatoes
INTO JAPANESE
昨日じゃがいもを食べて
BACK INTO ENGLISH
Eat potatoes yesterday
INTO JAPANESE
昨日じゃがいもを食べる
BACK INTO ENGLISH
Eat potatoes yesterday
You've done this before, haven't you.