Hello again @Sidra,
welcome back. You're completely right, the district government in Düsseldorf is competent for the recognition of school leaving certificates for people who reside in North Rhine-Westphalia. Documents and the application form can be sent by mail. You'll find a list of required documents here, and also the application form: https://www.brd.nrw.de/schule/schulrecht_schulverwaltung/Zeugnisanerkennung.html#top.
The adress and the person responsible for you can be found here: https://www.brd.nrw.de/schule/schulrecht_schulverwaltung/Zeugnisanerkennung-M_Ansprechpersonen.html
I hope my answers were useful for you and I'll be very pleased if you contact me again with further questions. I'm a member of the mbeon-staff and I‘ll be glad to guide over a longer period of time.
mbeon is an online advisory service for migrants via the mbeon-app, which you can download on your smartphone for free. You'll find me in the mbeon-app under my name München, Frau Müller and get confidential one-to-one advice in a safe virtual room where nobody can read messages. For further information please visit www.mbeon.de.
Download for Android: https://play.google.com/store/apps/details?id=de.zone35.mbeon
Download for iOS: https://apps.apple.com/de/app/mbeon-messengerberatung/id1408795643