the buyer back out after the downpayment but we have formal written agreement

Yung buyer ng rights ng house namin nagbackout, pinahold nya bentahan sabi nya sure na sila na bibili ng house wag na ibenta sa iba so we expect na sure buyer na sila, we vacated the house after they give downoayment then suddenly sabi nila wala na si mapoproduce na pera for the balance i still gave them 15 days pero talga hindi na daw nila kukunin then they want the money back. we are willing to return it but give us time to raise 50k. Then they harrassing us to return it as soon as possible. Can we forfiet the downpayment kasi sila nman yung nag backout sa agreement nmin, na dapat may buyer ako iba pinahold nila yung bahay then di pala nila itutuloy yung pagbili? Pwede ba nila kami idemanda?
Please i need an answer so badly.. thanks a lot