How can one atone for the sin of fornication and overcome sexual urges, given the difficulty of marriage and the necessity of interacting with a corrupt society?

Adultery is one of the gravest sins, and its perpetrator is threatened with severe punishment. If remaining in Europe endangers your faith, then you are obligated to return to Muslim countries immediately. If you wish to complete your studies there, then promptly marry a righteous woman who will keep you chaste from unlawful acts, for marriage can be a cause of abundant provision, and Allah has promised aid to those who seek chastity. It is not permissible to remain in non-Muslim countries without a wife while fearing falling into unlawful acts. Until marriage takes place, you must fast frequently, for it curbs desire. Avoid gathering with women, lower your gaze, and ask Allah for guidance, chastity, and self-sufficiency. Seek refuge in Him from the evil of hearing, sight, heart, and private parts. Be diligent in reciting the supplication upon leaving the house, and strive to befriend righteous, upright youth.