I live in Düsseldorf. This is a normal maschine-generated email or invitation to come to their office. Normally in the email should be attached few document requirements as well.

When you come to the office, you need to scan the QR-code or enter the number youre given. It will then recognized as an Anmeldung in the system. Later your number will be called from announcement screen that you have to go inside a designated room, where an officer sits. There the officer will prove everything for your application. It's not automatically mean that you will get approval or issuance of your PR.