sliderbl on "Failed to upgrade to WP 4.5, resulting a 500 server error"

Hi

24 hours ago I tried to upgrade wordpress as usual in the admin panel. It takes for a while and stop with the word "updating" without further progress.
So I reloaded the page, and since then I cannot access to all of my site content, including the admin panel.
All pages appear in a "500 server error".
I tried some methods like deactivating wp-content/plugin or removing .maintenance file via FTP, but these didn't work.
And I cannot replace the WordPress zip via FTP (some unknown errors).

My site is pinkslider.erufa.com/index2.php
Really frustrated.
Thank you very much for you help.