My site is http://imparareinglese.com/
The site displays fine, and I can log-in, but any attempt to use the dashboard results in a "page not found".
I have disabled all the plugins using FTP, which did not resolve the problem.
I disabled all the themes too, but that just resulted in a white screen. Renaming my my usual theme as another installed theme resulted in a change of theme, but no resolution of the problem.