NISSEN/PODSCH[C]K - Königsberg/Ostpreußen

Greetings!

I am looking for documents to support the existence of my great grandparents
were from Koenigsberg. All I have are their names, no birthdates, no former
addresses, nothing. I tried to get a copy of my grandmother's birth
certificate in the hopes that such information would be written on it,
but the Standesamt I in Berlin said they don't have her birth certificate.
I also contact the Kirchlicher Suchdienst in Stuttgart and they have no
records for my family as neither does the LKVA.

Great Grandfather: Gustav Nissen, mechanic - guessing he was born around 1895 -
1900
Great Grandmother: Frieda Nissen born Podschu[c]k.

This information came from a Meldekarte (Registration card) for my grandmother
from when she lived in Nuernberg.

Can someone also please tell me where I might be able to find Wehrpass
(draft card or service records) for Koenigsberg during World War I and
World War II? I hope that perhaps some family members were military because
then there might be records supporting their existence.

great grandfather - Gustav Nissen, mechanic by trade, probably born around
1895 - 1900
his wife's father, so my great great grandfather -

Wilck & Partner
Beratungsgesellschaft bR reports that they have a state railway record from
Wehlau, with an inspector last name Podschuck, no first name.

Thank you for any assistance.
Nichole