What is the ruling on marrying a Christian man who promises to convert to Islam, and is it preferable to marry a Muslim who is already married?

It is Islamically forbidden to date a friend or communicate with any man within the framework of a romantic relationship outside of a legal marriage, whether he is a Muslim or not. The sin increases if the man is a disbeliever. Marriage to a Christian man is absolutely forbidden, and it is a grave sin and indecency. It is not permissible for a Muslim woman to marry a disbeliever, even if he promises to embrace Islam, unless he truly converts before the marriage contract. One must repent from forbidden relationships, and if a Muslim woman chooses what is forbidden, she will reap its consequences. As for marriage to a Muslim man, his situation, religion, and morals should be inquired about. The fact that his first marriage has not been long is not an impediment to marrying him, as polygyny is permissible as long as the husband is qualified for it. One should perform istikharah (a prayer seeking guidance) regarding marriage to a Muslim man. However, with a non-Muslim, istikharah is not permissible for such a relationship; rather, it must be severed immediately.