Greek comedy film 1967, TH. VEGGOS

The kind-hearted Agathoklis gets into trouble because of his natural inclination to help others, often at the expense of his own needs. When he risks losing his wife, who is influenced by her mother, Agathoklis agrees to sign a deal to change his character.
As a result, he transforms into the complete opposite of his former self. Soon, he becomes frustrated with the lifestyle imposed by his mother-in-law and decides to get rid of her.