WordPress layout gone and no way to log in

Help,

I was trying to have wordpress to open on a page instead of a post, and added the /?page_id=31 part behind the domain in the general settings.

As that did not work, I put this part behind the domain in the field on top, but now my entire layout is gone.

It’s not possible anymore to log in or do anything, the site looks weird, as there is no layout. Reunloading the wordpress files did not work.

Anyone??