Hello Sir
As an electronics engineer, inventor and android developer with wide experience in this field and published apps on google play store i will be happy for working on your project.
my bid for building two apps not one ... the first will be for your clients with all necessary features and the other app will using for full control of the system with permissions to show clients requests , add categories and types under each one with pictures ..etc
both of two apps will connected with real-time databases system (firebase) for very fast response and synchronize with all devices ... add onesignal notification services to allow you send notifications to anyone download the app even if its close .. adding advertises from admob too.
hope to discuses more soon...
My regards.