I am currently dealing with the exact same situation here in australia with the apartments toilet above our bathroom.

They attempted to ‘identify’ the leak by cutting open the ceiling and now leaving the leak WIDE open to pour all over our floor.

I am not sure where a bouts you are from, but some sort of tribunal hearing can take place to force the landlord or person above to fix the issue.

They can generally solve the issue within 2 days.

Otherwise consult your local tenants union. They can point you in the right direction..