Build a CalDAV Calendar for Android (Android APP) (Important is to know CALDAV)

I need an Androip App Developer who knows how to develop a calDAV Calendar App. 1. The App should be an indipendend Calendar syncronised via CalDAV with an online Calendar (Account provided by me) Config / Design 2. Simple plain view (background picture should be customised by client), Views: Year/Month/Week/Day/Events=Agenda) 3. Event Color and Event Type(name) should be changable by user (Recuring, Birthday, Important Events (Client should be able to add own Eevents with colors too)) 4. Synch automation setting 5min,15min,30min,1hr,3hr,6hr, manually or by local change only 5. Support all calDav settings and fields (i.e. Event, Location, time from/to etc, Notes, Alert, Status, Recuring, Time Zone) 6. User should attach documents or pictures to (does not need to sync with calDAV(can be local only). 7. Add an Attendee should open forward menu like send via whatsApp/email/sms. 8. User should be able to customise Alert sounds. 9. You have to teach me how to adjust or customise branding for the App too. 10. Implement a License Module any Questions.. just ask. Hope someone has expiriences with CalDav