What is the ruling on dealing with heirs orally waiving their right to inheritance, and is it permissible to sell the share of one of the heirs without his knowledge, and how is the price of the real estate determined for the inheritance in this case?

The estate of the deceased, if limited to two sons and two daughters, is divided such that the male receives the share of two females, in accordance with the noble verse: {Allah instructs you concerning your children: for the male, what is equal to the share of two females}. Thus, the estate is divided into six shares, with each son receiving two shares, and each daughter receiving one share.

As for the price of the house, it is to be estimated by real estate experts, not by the buyer. You are permitted to ask the heirs to consider you in the price, but you do not have the right to compel them to do so.