What is that a screenshot of? It looks like it’s showing the encoding of the website itself.
Your database can have a windows-1251 encoding while the website itself uses something else entirely.
If you want to change the default character set for a web site, you can go into Services -> Configure Website -> Languages, and there you can set “Character set for documents”.
My website is running in shared hosting, everything is fine.
But after move website to Vps with Virtualmin, Encoding is “UTF-8” :
I don’t know how to change Encoding from “UTF-8” to “windows-1251”. I already changed “Character set for documents” in Virtualmin to “windows-1251” as you said, but it does not work.