YOU SAID:

私は確かに私は確かにそうだ

INTO JAPANESE

私は確かに私は確かにそうだ

BACK INTO ENGLISH

I am sure that I certainly did

INTO JAPANESE

私は確かにそうしたと確信しています

BACK INTO ENGLISH

I certainly believe I did so

INTO JAPANESE

私は確かにそう信じました

BACK INTO ENGLISH

I certainly believed so

INTO JAPANESE

私は確かにそう信じました

BACK INTO ENGLISH

I certainly believed so