γραμματέας masc. and fem. forms are the same? ο / η γραμματέας are both correct?
Yes, it happens with other nouns , ο/η δικηγόρος lawyer, ο σύζυγος husband , η σύζυγος wife.
That's odd since both "η' and "ο" have been in the incubator from the beginning. Oh, let me ask: was this on the Tree, or Strengthen skill, or test out. It will help if you let us know.
"Ο δικηγόρος και ο γραμματέας του¨...
You used the wrong word.
Ο δικηγόρος και η γραμματέας του.
Meaning: The lawyer and his secretary.
A "secretary" can be male or female all that changes is the article unless there is something else that is incorrect. Please let us know; we take care to have the course correct.