It is a good practice to create a backup version of your website before updating the theme, in the event something unexpected.

The simplest way to update a theme is via the Restore  which provides a reliable way of updating a theme in most cases.

However, this method is known to cause issues by overwriting some crucial Codes, widget, gadget, on occasion, in this case, the users would, of course, they will present a deformation in the themes.

The recommendation we provide is to create a secondary blog and upload the theme, customize and configure it before uploading it to your blog.