Delay loading custom page

Hello everyone,

           I'm new working on Vaadin framework and when I started an internal new project in my company I found a problem I was not able to solve. For my login page I created a CustomLayout in order to use the graphical design defined by my company, which uses a couple of CSS files and JS files. I created my UI by pointing to my specific settings with this annotation: @Themes("my_stylesheet") and @JavaScript to point to the JS files.  Under VAADIN/themes/reindeer I created the style.css file, I defined my background image there and I imported the CSS files used by my page (by using @import). 
The point is that I was able to start my login page with all the styles I wanted but I realized that there is a delay (6-8 seconds) when the page is loaded. It does not happen when I run the same page by using just HTML code (without using vaadin framework), the page appears quickly without any kind of delay.  
I know that with this framework we have to process the code in the backend but I think it is too much delay (by comparing this behaviour with my test using HTML). Is this correct? Because it also happens when I click refresh in the browser. That's why I considered it weird. 

Could anyone please help me with this? Because I tried a lot of alternatives around it but I could not improve this.

Thanks in advance,

Luis.

Hey Luis,

Not sure if it'll work, but you should be able to check what's going on using Chrome, right-click > inspect > Timeline.