Do you have other useful content(post, images..) on your website?
please reset the website by a plugin [ https://wordpress.org/plugins/wp-reset/ ] if there is no useful content, because it will reset all content.
Please import again, make sure “Import Origin Images” is picked up.
There are 504 issues when I selected the “Import Origin Images”.
Could you please send website FTP account. I need to check more things.
If It still failed, I could import the database directly, but it will cover all current database including user data. But don’t worry, I will re-create the user. Do you permit to import the database?