Getting out of a contract to sell

Hi.. Hope u can give me some legal advise. My name is anton from kabankalan city negros occ. My issue is that my family signed a contract to sell without the presence of a lawyer and it was notarized. Is it a valid contract? Can we get out of that contract? We no longer want to sell the property. Its only now that we discovered that the offer was too low compared to the zonal value of the bir. Also one of their stipulations is that they will use the property upon giving us the earnest money of only 350k. The value of the transaction is about 24m. We were unable to see this during the time we signed the contract and no lawyer was present to explain this to us. ALSO during that time my mom just died and we are in financial crisis looking for money for her estate. This stipulation seems malicious to us and we really want to cancel the sale. Thanks and hope you can assist us.

answered your other post