Hello Everybody,
My issue solved! 
The main problem was that Blogger has no instruction information what to do / how much time should wait.
So after you purchase a custom domain from a third party service and integrated it to your Blogger interface:
- You have to wait 12-24 hours.
- Then a notification is appear at the top of your Blogger interface: "HTTPS available".
- Then you can turn on HTTP. It will be in "PENNDING" status.
- You have to wait anither12-24 hours.
- HTTPS redirection will be active, you can turn on.
- Your site will be validated for HTTPS.