404 page for Blog page

Hi!

I faced a problem of the second 404 page on my site.

I've already created and designed a 404 page for my site.

But when the incorrect link contains "post", leading to one of blog publications (e.g. https://randomsite.com/post/nameofthepostwhichdoesn'texist), then I see this message, which said that Page couldn't not be found, watch another posts in our blog and button leading to blog (the screenshot is in Ukrainian).

How can I turn off this page or customize the message in it?