Is helping a Muslim answer sexual questions pertaining to women considered haram, or is it for the sake of knowledge and problem-solving, especially if he lives in a non-Muslim country?

A Muslim should occupy themselves with what benefits them in their religious and worldly affairs, and avoid speaking about sexual matters unnecessarily, especially if the discussion is about a specific person or involves disclosing a secret. It is permissible to speak about such matters for a legitimate, recognized religious purpose, such as when a woman speaks with another woman about this topic for general benefit. This falls under the Prophet's (peace and blessings be upon him) saying: "Whoever among you is able to benefit his brother, let him do so."