?edit just shows white box


when trying to access the ?edit page on royalblue-esports.com it just shows a big white box on the right with the page on the left.

Is there a way to destroy the CSS of the editor somehow?
Did I do something strange?

It would be amazing if someone could help me here.

Thanks a lot!

Here is my site Read-Only: LINK

Any ideas for my problem? :S