How can I repent with a sincere repentance and rid myself of the burden of money and properties (lands, car, house) acquired from drug dealing, knowing that my sons are still engaged in this trade, and I have not abandoned prayer, fasting, and Hajj throughout my time working in this field?

You have wronged yourself and exposed it to the wrath of Allah. Your duty is to hasten with sincere repentance to wash away the burdens of what has passed, for the door of repentance is open and will not close until the sun rises from the west. No matter how great the sin, Allah's forgiveness is greater, and His mercy encompasses all things. Allah Almighty says: "Say, 'O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allah. Indeed, Allah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful.'" and "And He is the one who accepts repentance from His servants and pardons sins, and He knows what you do."

Among the conditions of your repentance are: ceasing the sin, resolving not to return to it, regretting what has passed, and disposing of ill-gotten gains by placing them in public welfare for Muslims or giving them to the poor and needy. If you are poor and in need, it is permissible for you to benefit from it to meet your needs, and you must dispose of what exceeds your needs.