Termination of a property SPA due to COVID-19 situation

I have made a 20% down-payment against an off-plan property in 2017. The sale & purchase agreement does not include a "Termination/Refund" clause and the property is due for handover by the end of the month.

The property value has dropped by 40% and I'm able to only get a mortgage for 80% of the current value. However, due to the current situation and the impact of COVID-19 financially, I'm not in a position to proceed with the remaining instalments.

I have to forfeit the contract as the developer has not given me any options for deferral of payment and has declined the request for a delayed handover.

Please advise if and how I can get a refund on the 20% amount that has already been paid upfront.