Please read This Theme Installation Tutorial First: https://d5creation.com/themeinstall/
Extend Version will be installed as a New and Separate Theme. You will have both Free and Extended Versions installed in your WordPress if you don’t delete them by yourself. You can switch back to any Theme anytime. WordPress dynamic data like Posts, Pages, Menus, WidGets, Settings are stored in a MySQL database, not in any Theme Files. So, Theme Installation, Changing, Removing don’t affect the site if you don’t modify/customize any Theme File directly.