vpn user internet access via another vpn user with NAT

[Lamask]

Initial data:
There is an Android mobile phone and a Windows 8.1 personal computer. The phone and computer are in different cities and use different Internet providers. Both the phone and the computer are connected to the Internet through NAT and have gray dynamic IPs without the ability to forward ports to them.
There is a Debian cloud server with a static IP address.
How can I, on an Android phone, after a VPN connection, access the Internet through the personal computer's ISP (so that the PC is the gateway to the Android phone)?

So that the Internet "sees" the android phone with the external IP address of the personal computer.

[Lamask]

In a normal situation, one could install an OpenVPN server on a PC and connect to it from an android phone. But the difficulty is that the PC does not have a white IP address and there is no way to forward ports to it.

[TinCanTech]

Connect everything to your central server.