Azure Application Gateway 502 error

I being working with the Azure application gateway (AG), and stuck at the following error. Here, my Network Diagram 

Here, the powershell script which I had configure Poweshell Output PS C:\Users\shabbir.akolawala> Get-AzureApplicationGateway sbr2appgateway

Name          : sbr2appgateway
Description   :
VnetName      : Group Shabs-AppGateway2 sbag2vnet
Subnets       : {sbag2subnet1}
InstanceCount : 2
GatewaySize   : Small
State         : Running
VirtualIPs    : {104.41.159.238} <-- Note IP Here
DnsName       : 01b9b0e4-4cd2-4437-b641-0b5dc4e3efe7.cloudapp.net

Here, public IP of the application gateway is 104.41.159.238 Now, if I hit for first time you hit the gateway, you get following output Note, this website doesn't render correctly, as many request (css/images) fail with 502.

Now, when if I hit this second time, I straightway get the 502 error

But, when hit the cloud service IP, I get my website correctly

I had configure the Azure Gateway with following configuration in XML file

https://drive.google.com/file/d/0B82YM4GuTaE0UXVRYjZTYzY2aFk/view?usp=sharing

My Questions are, 1] Do one have an idea how to access logs which are generated in Application Gateway (In theory, Application gateway runs on IIS 8.5 / ARR)

2] Or any obvious error which I made in design or AG configuration?