Proxy/VPN Server on Android/iPhone optional xamarin

The project is to create a proxy / vpn server on a mobile phone. Use the cell phone as a proxy server to use its connection to make requests on a particular api. If you have any technical details that should be added, I am open to suggestions. More details send me on chat. ---------- There are services on the Internet that do this, where the mobile device or the browser (desktop) becomes a server of the connections making it remotely I use the IP of the proxy server to make connections in an API in the internet. ---------- What I need: On my server I run an application where it must communicate with an API. However I can not use the IP of my server to communicate with this API, I have to use the IP of the user's mobile device to make connection with API. I will need to dynamically connect to these devices.