Blank site, no plugins, no widgets, no themes in dashboard

Hi,

I have a WordPress site, and it has been running just fine until now. An evening I sat and were about to make some changes to my site.I had filezilla opened but I didn’t do any changes(on purpose), only looking around. But then, when I wanted to enter my site, I couldn’t. Just got an annoying blank page. Then I logged in to my wordpress dashboard and I saw that all my plugins, widgets and themes were disappeared. I opened filezilla and found all the folders with the missing things in, but I just don’t get why they are not displayed on my dashboard? Please help me. This is driving me crazy! It should be said that I am new to WordPress and making websites.