Hi Moutasem,
Go in your App -> App Settings -> Configurations -> Server (second tab in the popup)
In this configuration you can specify the port on which the application will run.
Default runtime port is 8080, but you change it to 8085 for example. This has no negative consequences.
Hope this helps.
@Moutasem Billah Rajab
I think Port 8080 is already in use.
You can kill the port 8080. I hope below Screenshot will help you to kill the port.