"I know the private road."
Translation:אני מכיר את הדרך הפרטית.
Was it a typo, or they rejected the sentence? If they rejected it, it means that you had more than one mistake. When there is one mistake, it usually counts it as a typo.
No, Duolingo is not just for male learners. It has many different sentences, sometimes insisting one one gender, otherwise insisting on the other. Don't read too much into it. It's just exercise.