Single NIC RRAS VPN/NAT Server traffic problem

Hello,

Background:

Recently we migrated to Microsoft Azure and i have successfully configured 3 server as

Server 1 : AD, DNS               10.0.3.4

Server 2 : RRAS with NAT     10.0.3.5

Server 3 : File server            10.0.3.6

 and we deployed Site to site connection for on-premises and everything working fine

Problem:

I have a few client they work from outside So, I install and configured RRAS server

RRAS server has single NIC and configuration done with "custom configuration" using this link : https://blogs.msdn.microsoft.com/lighthouse/2013/07/30/how-to-deploy-sstp-and-l2tp-vpn-in-windows-azure-windows-server-2012/

Now i have two problems

1. RRAS Client can't able to ping Server 2(RRAS Server) 10.0.3.5 but they can ping Server 1 & 3 (10.0.3.4 and 10.0.3.6) successfully
2. Server 1 & Server 3 can't able to ping RRAS Client

This is my current diagram

Kindly guide me to solve this problem