how to remove an "invisible"page

Hello,

I have a weird problem. I want to remove a page, which isn't visible in the upfront pages section anymore. Neither can it be found in the pages of wordpress.
Still it is visible at the front end and can be edited with upfront.
It is the homepage.
I couldn't change the permalink. It kept repeating the name of the page after the URL and that was not what I wanted. Somehow I was finally able to delete the /pagename, but now the whole page isn't visible anymore in upfront page settings.
I can't edit it for SEO now. Creating a new page gives the same problem, repeating the pagename. Also I'm curious if upfront is compatible yet with Yoast. My SEO specialist wants to work with Yoast. With two pages she filled in and I see things happening in upfront, but not sure if it'll work.
Help !