Must the questioner return the money he took from a woman who paid half his salary without his knowledge? Is this money considered unlawful (haram)? And what is the ruling on marrying her to settle matters, knowing that she does not adhere to the explicit [religious texts]?

The question implies that the questioner has fallen into several forbidden acts, including: establishing an illicit romantic relationship with a foreign woman, committing adultery with her—which is one of the greatest sins—and lying to her and defrauding her to take her money. He must repent from all of this and return the money he took by fraud. As for the money she willingly paid due to the relationship, he must dispose of it by spending it on charitable causes. Regarding the job, if the field of work is permissible, there is no harm in continuing with it, and he is entitled to his wages from the employer; it is not related to the fact that part of the payment was made by the woman. As for marrying this woman, since she is not religious and of good character, the questioner is advised to leave her and seek a righteous woman who will assist him in his religious and worldly affairs.