YOU SAID:

My coworker is hard at work at his desk next to me

INTO JAPANESE

私の同僚は私の隣の彼の机で仕事に熱心です

BACK INTO ENGLISH

My colleague is enthusiastic about working at his desk next to me

INTO JAPANESE

私の同僚は私の隣にある彼の机で働くことに熱心です

BACK INTO ENGLISH

My colleague is keen to work at his desk next to me

INTO JAPANESE

私の同僚は私の隣の彼の机で働くことに熱心です

BACK INTO ENGLISH

My colleague is keen to work at his desk next to me