How to connect via HTTPS to Yandex.ru via OpenSSL?

Question

C++ / C#

Hello!

I work with Boost::asio, connected OpenSSL. How can I now connect to sites using a secure connection?
With http, the connection is successful. But it doesn't work with Https.
I was guided by this article: https://habrahabr.ru/post/271203/ but it tells about issuing a certificate for your own server.

The main question is how will the web client (which I am writing) connect to the site via https, besides Yandex? Where to get a certificate?

When I generate the certificate myself and connect, I get the following messages:

Verifying /C=PL/O=Unizeto Technologies S.A./OU=Certum Certification Authority/CN=Certum Trusted Network CA
Handshake failed: certificate verify failed

If you try via http:
Handshake failed: stream truncated