What is the ruling of the Shari'ah regarding marriage for a man who has reached 35 years of age, is unable to marry due to lack of money and high dowries, lives with his family and cannot build a house, given that his country prohibits Islamic banks? Is it permissible for him to borrow from conventional banks for building and marriage?

The Prophet, peace and blessings be upon him, advised young people who are able to marry to do so. As for those who are unable, they must practice abstinence through fasting, lowering their gaze, and staying away from temptations, as indicated by the Quran and Sunnah (definition). A Muslim is either able to marry or unable to. The one who is unable must practice abstinence through fasting and other means until Allah facilitates their affairs. Young people who are able to marry should exert the necessary effort for it and avoid flimsy excuses that prevent them from marrying, such as living with family, waiting to build a house, finishing studies, or having a high salary. Usurious loans from banks are forbidden, and taking them for building or marriage is not considered a legitimate excuse. The hadith (definition) you mentioned, "Treat young people well, for they are the pillars of the Ummah," has no basis in the books of hadith.