view problem with post(s)

I have a website with pages and I think I removed the “home” page, where the posts were, by accident. I do not even remember how and when I did it.
Now I was creating a possibility for someone to put posts on the website, just doing posts. So I tested it and uploaded the post and than I wanted to view the post and I got a 404 message, page not found. Sounded reasonable as I had removed that page and as I do not know how to get it back I decided to use “post Pages” in Read settings.
Now, every time there is a new post, he arrives nicely in the page I appointed as the post page, BUT ……. when I have uploaded the page or see the index of the posts for administration purposes and try to view one of the posts I still get my 404 message, because the url is very strange:
http://www.ambalahaye.nl/http:/www.ambalahaye.nl/sample-post/

This is what I get as an url when I do a view. A double website name and the page “sample-post”
Can somebody please help me out with this?

Kind regards

Evert