Updating a WordPress Theme
Before updating any WordPress themes, we highly recommend you to back up your current site in order to prevent any loss of settings and/or customizations that you've made. There are two ways to update your theme: automatic update and manual update.
Remember, a new theme update will replace the old files of the theme. If you’ve made changes to your theme’s file, then you’ll lose those changes if you update your theme. So, for heavy theme changes, you should be editing your theme in a child theme. This allows you to upgrade your theme in the future without losing the changes you have made to the parent theme files.
It is possible to update your theme within WordPress Dashboard with one click by using automatic updates. Note, not every WordPress theme provides such functionality. In this case, you'll need to update your theme manually.
If the theme supports automatic updates, navigate to Appearance → Themes and click on the current theme. Any themes that have updates available will display an alert banner. From the banner area, simply click o the Update Now link to complete the upgrade.
Many theme providers require the user to manually update the theme. The easiest way to do it is to upload your theme via WordPress Dashboard. Note, WordPress does not allow to have a theme folder on your server with the same name as the folder inside your uploaded zip file. In short, you cannot have two identical theme folders on your server.
In this case, from your WordPress Dashboard, navigate to Appearance → Themes and activate a different theme. If you have done any customizations to your theme files, these customizations will be lost if you use this method. Choose to delete files of the theme you want to upgrade. Then upload the newer version of the theme and activate it.
Also, you can try Easy Theme and Plugin Upgrades plugin that allows you easily upgrade your themes and plugins using zip files without removing your current theme or plugin.