"I am trying to put the key in the door but it's not working."
Translation:אני מנסָה לשים את המפתח בדלת אבל הוא לא עובד.
I don't quite remember learning לתוך. This "mark all correct translations" is not a very good feature.
Sometimes we put some non-learned words as a possible best answer by mistake. So they appear in that exercise. When we come across them, we remove them. Anyways, thanks for reporting!