Install SSL Certificate for Docker Container on EC2

We are running an NGINX Server on a Docker Container which is hosted on an EC2 instance. Our Domain is registered with Amazon Route 53 but it seems like, there is missing an SSL Certificate on Docker or on EC2 instance.

The message is as following when we curl our Domain -

* Connected to <<our domain>> (<<our IP of EC2 Instance>>) port 443 (#0)
* ALPN: offers h2,http/1.1
* (304) (OUT), TLS handshake, Client hello (1):
*  CAfile: /etc/ssl/cert.pem
*  CApath: none
* LibreSSL SSL_connect: SSL_ERROR_SYSCALL in connection to <<our domain>>:443
* Closing connection 0
curl: (35) LibreSSL SSL_connect: SSL_ERROR_SYSCALL in connection to <<our domain>>:443

it works fine on http..

I tried to install with CertBot on our Docker Container - like this Tutorial . I can't even install snapd - Unable to find package.. on updating the Debian, I get there's no updates possible..

Any Recomadations? Thanks a lot!