ASP.Net Error: 504 (Timeout while reading response from Server)

I am trying to upload bulk data through excel (around 19K entries). It throws "Site took too long to respond" error after some time. How can I stop it. I am reading excel row one by one in MVC action method and adding or updating data in DB by Entity framework

I have set 

<httpRuntime targetFramework="4.6.1" executionTimeout="9999"/>

but it is not working either.

I have set execution timeout 600 seconds in web.config and also in Connection timeout to 600 in IIS web site application setting.

It is still throwing "504 (Timeout while reading response from Server)" error after 1 minute