Possible solution

Besides what is written above, there could be some other solutions, too.

Generally, a contract is effective after all relative parties sign the contract. But, under certain conditions, a contract is void even when the contract is signed. These conditions include, but not limited to, one party is misled by certain information, or the party does not have the capability to understand the contract or consequences.

You can argue that your father does not have sufficient language skills to fully understand the contract, or he was misled by the other party, which would help the judge determine that the contract is unfair and void.