Is it necessary to inform one's fiancée about a slight penile curvature before marriage?

What you have mentioned is not considered a defect that prevents a man from having intercourse with his wife, and you are not obliged to inform the woman you wish to marry about it. You must also not speak with your fiancée except out of necessity and in the presence of one of her mahrams; because she is still a stranger to you until the marriage contract is concluded.