If you are looking for a for iOS, popular and verified options include: Das Telefonbuch : The official German directory app. Truecaller : A global caller ID and directory service.
Based on the structure of the string, it likely refers to one of the following: monument2-telefonbuch-ipa
In iOS development, an .ipa file is an application archive. "Telefonbuch" is German for "phone book" or "directory" . This specific naming convention suggests a custom-built or archived phone directory application, possibly a second version (monument2) or part of a series of historical digital preservation projects (monuments). If you are looking for a for iOS,
If this is a bespoke "monument" project meant to digitize old phone books for a museum or archive, it would not have public "reviews" in the way a commercial app does. "Telefonbuch" is German for "phone book" or "directory"