Widgets, Trojan, can't upgrade

Hi all,
Please could someone help me? I have a number of issues. I tried to go onto my website but Bitdefender said it had a trojan, so I’m trying to find out why. When I finally went onto it I found I could not upgrade to the new version of WordPress – it tells me Could not copy file.: wp-includes/images/crystal/document.png

All my plugins and everything else are sorted.

Then I found that for some reason I can’t access Widgets – it no longer appears under ‘Appearance’ on my dashboard. I activated a new theme to try to solve the above problem and all my widgets disappeared.

So in a nutshell, what is the trojan thing, how do I get rid of it, how do I upgrade to the new version of WordPress and where are my widgets? My site is at http://www.popspeaking.com

Regards, Gaynor

https://wordpress.org/plugins/website-toolbox-forums/