Deleted files accidentally

I bought Highend through Mojo Market place, thinking it would be easy to modify to create my own website which is very simple. I am selling myself and not any product so I do not need about 95% of the content in Highend. However, I would like to get the web site up and running quickly but I think I’ve messed it up. Would it be possible to re-install the theme. I understand that it is better to use a child theme to preserve the original for future updates. And this time I will simply follow your guides. By the way, do I need to load a demo version? If so why? Is it just to see what the original looks like? Which demo version would be more suitable for my simple needs which is to have a website where I will address, several different categories of blogs and these should be selectable from the Main menu. I would appreciate any help you can give me.

Many thanks

Barbara