Domain on heroku?

Question

Heroku

Good afternoon. Having written the application, I needed hosting, the choice fell on heroku because I tested my application on it, and I just like it. But I ran into some problem.
First, I bought a domain on mnogodomen and made settings in "DNS zone management":

Then I added a domain on heroku (Hosting version is free):

And in the end I get this:

Answer 1

• Firstly:
  It is not clear why you specified an A record if the manual says that you need to make an ALIAS or CNAME record
  
• Second:
  Tried this: https://devcenter.heroku.com/articles/custom-domai... ?
  Via cli tool
  

  heroku domains:add example.com
  Adding example.com to ⬢ example-app... done
   ▸    Configure your apps DNS provider to point to the DNS Target
   ▸    whispering-willow-5678.herokudns.com.
   ▸    For help, see https://devcenter.heroku.com/articles/custom-domains
  
  The domain example.com has been enqueued for addition
   ▸    Run heroku domains:wait 'example.com' to wait for completion

  
  As a result, you need to add an ALIAS or CNAME pointing, for example, to hidden-sierra-7936.herokudns.com (here you specify your application)