I am currently filling an application form of a housing agency and it has a question "Wurde die bisherige WNG gekundigt?" and when I translated, it is shown as "Was denounced former WNG".

But really not able to understand what it means. Please help.

It means, have you yet informed the owner/manager of your current apartment that you will be leaving

Thank you so much Jaudi

I know it is an old thread.

Wurde die bisherige WNG gekundigt? == Is the contract of your former apartment terminated?

Possible answers:
No. (This means you have to show financial means to pay rent for both apartments).
Yes, by me. (The usual case)
Yes, by landlord because [renovation/new building/self use by landlord]. (Also usual cases)
Yes, by eviction due to [unpaid rent/noise/disturbance]. (Not an usual and complicated case, good luck with finding a new home)