YOU SAID:

today were going on a picnic so do you want to come

INTO JAPANESE

今日はピクニックに行っていたので来たいですか

BACK INTO ENGLISH

I went on a picnic today so do you want to come

INTO JAPANESE

今日はピクニックに行ったので来たいですか

BACK INTO ENGLISH

I went on a picnic today so do you want to come