It is not clear to me whether money brought into the marriage by my wife, i.e. deposit on a house, has to be repaid by me. In the USA money brought into the marriage and used as a deposit for example, is considered as a gift and becomes joint property. Is Russian law the same?
Probably I don’t quite understand your question. If the moneys were earned in marriage, they become a joint property if spouses and have to be divided in equal parts. If the moneys for down payment were received from selling of other property owned by your wife before marriage, her part in the join estate increases respectively. In any case this is not ruled by Russian law because the property is abroad.