Website cyclically down and I can't login

Hi there! This morning I tried to make a new POST on my website but there was no text editor and this message was written there: “You are currently editing the page that shows your latest posts.”.

Then I tried to publish a new PAGE. The text editor was there but the publish button was a “submit for review” one although I was logged in as administrator (and the only user).

For this reason I logged out in order to see any changes in the permission when logged in again, but the login panel just refreshed the page when I inserted the right username and password.

Every time I try to login with correct username and password, the website goes down. After a few minutes it is up again. I realized that the website starts to go down cyclically every few minutes, and when it works I cannot login.

I recently updated wordpress to the latest version (4.3.1). Has this anything to do with it?

Now I’m out of the dashboard of my website and the FTP is the only thing I can actually control.

I tried all the solutions suggested by wordpress support. (disabling plugins, deactivating the theme, editing the user’s table, creating new login file)

Any other suggests?