Un-import templates?

I’m setting up a brand new website and thought I would play around with the templates offered by Gutenberg. Unfortunately I didn’t realize that by clicking on “import site” for a couple of different templates I would create a huge mess!

I haven’t put anything into the site that I need to keep, the whole thing is just a sandbox. So really what I’d like to do is just get rid of all the templates / “sites” I imported. Is there a way to do that??

I tried just deleting the pages; but there’s other bits of content floating all over the place and it’s proving difficult to find it all… Thanks!

The page I need help with: [log in to see the link]