YOU SAID:
Yesterday I was playing chess
INTO JAPANESE
昨日はチェスをしていた
BACK INTO ENGLISH
I was playing chess yesterday
INTO JAPANESE
昨日チェスをしていた
BACK INTO ENGLISH
Was playing chess yesterday
INTO JAPANESE
昨日チェスをしていた
BACK INTO ENGLISH
Was playing chess yesterday
That didn't even make that much sense in English.