there are numerous ways to achieve what you want… I would create a new folder in the Pages section and drag all the pages that you want to use in there.
You can designate any page you chose to be your homepage - you can do it by going to the Pages section however on the page you want to make your homepage and click the gear icon - you will see options there – you don’t need to delete anything untill you have prepared you site completely… then you can remove unneeded / unused pages/elements
it seems that in your template the footer/navbar elements are symbols so to use the one you like is as simple as copy/paste it to the page you want to use it on. alternatively go to the Add panel and select the Symbols tab - you will find them all there