Route hotspot clients through VPN

[Doro1981]

Hi,
I am trying to route the traffic of my hotspot clients to the VPN server network. Without success til now.

Server network is 192.168.1.x
VPN Server 192.168.1.2 (SSTP)
VPN Client is 192.168.1.101 (Mobile phone)
Hotspot (Mobile Phone) is 192.168.43.1
Hotspot Clients are 192.168.43.x

Accessing the server network from the mobile phone works. Accessing the internet from the Hotspot clients works well.
But there is no access from the hotspot clients to the VPN server network (192.168.1.x).
Do you have any idea how to achieve this access?

[admin]

Android not allow to use the VPN through tethering.
Maybe you can find some workaround on Google, but surely it require root access because the workaround must change iptables/advanced routing configuration.