YOU SAID:
last night I saw my friend eat ice cream
INTO JAPANESE
昨夜、友達がアイスクリームを食べるのを見ました
BACK INTO ENGLISH
I saw a friend eating ice cream last night
INTO JAPANESE
昨夜友達がアイスクリームを食べているのを見た
BACK INTO ENGLISH
I saw my friend eating ice cream last night
INTO JAPANESE
昨夜友達がアイスクリームを食べているのを見ました
BACK INTO ENGLISH
I saw my friend eating ice cream last night
You've done this before, haven't you.