Malware found on my site

Hello guys,

At first I’d like ot inform that I’m not a IT/programming specialist ??
Yesterday when I was preparing new post to my page, but at some point I found that:
– there are missing fields on edition page -> https://oi62.tinypic.com/sg7tk0.jpg
on right side there are missing eg. categories field, etc.
– when tried to save draft, it kicked me to main wp-admin page, and there was no new draft,
– i saw growing numbers of spiders to my web – what are those? -> https://oi61.tinypic.com/sfgjkm.jpg
– and finally i cannot play with plugins and everything (cannot deactive plugins, turn off widgets, change them, nothing).

So far this page is like a demo, when there is nothing allowed to be changed ??

Then looked for this page -> https://sitecheck.sucuri.net/results/www.aviatore.pl
and found that some malware are on my site ??

Erased all files which contained <script type="text/javascript">eval(fun ));</script>, re-installed wp-admin (erased from FTP and upload new one),
and still issue is visible.

I got no idea what should I do?

My first thought would be to make a backup, but it so those files might be affected ??

Please help …
Thanks in advance