At the moment, I need to create an app that will dynamically change it's sections

This is the app layout.
The main section would be an independent webapp, because it would keep changing it's contents. The nav bar it's basically a set of images that work as buttons and change the contents of the main section. The side bar have some parallel uses, but it can work with the "main webapp" (the one that contains all sections
That's why I think having a nested webapp would be the best solution. I tried google site but since I can't really control it I dropped the idea. But it's possibly to achieve that? At the moment the app need to refresh the whole page to apply even the smallest HTML change
Im a little confused, You could have that part dynamically generate information in the main section and everything else be static.
And the web app will update anytime you change the code weather its a small html changes or logic changes. unless its deployed and you dont have sync on, then you need to manually sync it to show the changes.
Update: I solved my issue stacking divs and changing the active one by hiding the others. I also using an include with my templates, in a way I can split my HTML code in a main template.
I use two types of includes:
function include(filename) {
return HtmlService.createHtmlOutputFromFile(filename).getContent();
}
And
function includeTemplate(template) {
return HtmlService.createTemplateFromFile(template).evaluate().getContent();
}
one used to include static HTML and other dinamic HTML (templates)