Hi mate.
Big note: Before updating or changing anything, pls backup both of your database + source-code.
I will show you the two ways to update theme: Update whole theme or update theme version. You can choose one of them.
1. Update whole theme. If you do not customize anything in sour-code on every files, I recommend you to update whole theme, it is very fast and easy way.
+ Step 1: You need to download the attached-package from Themeforest Supershop-v x.x.x.zip file. This zipped file contains the folders " modules" and "themes"
+ Step 2: Upload this zipped file to the root folder of your website via ftp or Cpanel, then extract this zipped file directly on your site, so the changed/updated files in these folders will be overwritten automatically ,...
+ Step 3: Clear cache of your site (in the backend).
2. Update theme version.
+ Step 1. You need to download the latest updated-package from Themeforest, then Unzip this zipped file. In the extracted folder contains two folders: modules and themes
+ Step 2. If you are using too old version, you should step by step updating theme versions without skipping any versions. Following the change-log (http://kute-themes.com/prestashop/supershop/changelog_supershop.txt) to upload and replace all the needed files... to the same path on your site via ftp or Cpanel. So the changed/updated files will be overwritten,...and new files will be copied into the correct positions,...
+ Step 3. Clear cache of your site (in the back-end).
Regards!