YOU SAID:

I heard this guy is doing the worlds first head transplant

INTO JAPANESE

私はこの男が世界初の頭移植をしていると聞きました

BACK INTO ENGLISH

I heard that this man is the world's first head transplant

INTO JAPANESE

私はこの男が世界初の頭部移植であると聞いた

BACK INTO ENGLISH

I heard that this man is the world's first head transplant