YOU SAID:

I came to the grocery store and bought a banana.

INTO JAPANESE

私は食料品店に来て、バナナを買いました。

BACK INTO ENGLISH

I went to the grocery store and bought some bananas.

INTO JAPANESE

私は食料品店に行き、バナナを買いました。

BACK INTO ENGLISH

I went to the grocery store and bought some bananas.