YOU SAID:

I'm sitting behind my desk thinking about that girls behind

INTO JAPANESE

私は自分の机の後ろに座っている

BACK INTO ENGLISH

I am sitting behind my desk

INTO JAPANESE

私は机の後ろに座っています

BACK INTO ENGLISH

I am sitting behind the desk

INTO JAPANESE

私は机の後ろに座っています

BACK INTO ENGLISH

I am sitting behind the desk