Auto Update your theme using WordPress
The WordPress 5.5 update expanded the content management system’s auto-updating capabilities to themes and plugins.
1. Download the latest version of the theme you want from your downloads area
2. Navigate to your site installation under Appearance→Themes and click on add new
3.Click on upload theme:
4. Add your theme archive (zip) file:
5. In the next screen that will appear select to replace the theme:
That’s it! This will update your theme with the new version.