Serwer error (400vbad request)

I have a problem with the site project which I was creating in Elementor. For the project needs I’ve created a subdomain with /test added to the address. When I finished basic project I wanted to replace the domain with the final address. After replacing the url some issue appeared and now I cannot do any update in current projects. When I click on “save changes” I receive information that there is serwer error (400 bad request). Even if I want to make new site project I can only add few sections 3-4 and than again I am blocked with this message. I was trying to copy elements from current projects and paste it to new, but there is the same situation. I can copy and paste 3-4 sections and than again I am clocked. Do you have any idea what I can do instead of reinstalling wordpress and do everything once again? I had only few small changes to apply. Can enyone help?

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