Building VoIP System with Webpanel + App based on Sipgate API

Dear freelancers,

we are planning on building a small webpanl with mobile apps to connect phone numbers and make calls.
The webpnale should be used as "administration" to add new phone numbers and new users. Users can then login in the smartphone app and make/ receive phone calls with the phone numbers that where connected to them by the admin.

Important features:
Admin Panel:
- Add new users
- Add phone numbers
- Connect phone numbers to users
- Connect one phone number to multiple users
- Record phone calls

App:
- Login for users
- Make/Receive phone calls with the connected numbers

ACCEPT CALLS: You can use our push APIs (webhooks) to take calls, among other things. You will receive newCallEvents and optionally follow-up events on a URI you have specified yourself, which you can handle accordingly. At this point you can also use the Real Time Call manipulation or / rtcm of the REST API to receive active callIds and, for example, to forward the corresponding calls or to issue announcements.

CALL INITIATION: You can initiate new calls via the REST API endpoint / sessions / calls and influence them further via / rtcm, just like when accepting calls.

This calling provider must be used:
https://www.sipgate.io/

You can find the exact requirement (Documentation) + the UX Design in the attached zip file.

Adobe XD Files can be viewed for free with this tool:
https://drive.google.com/drive/folders/1Y6hm7hy7ILS2OtdkA1gG15asuOv0maNy?usp=sharing