I’ll try another approach. Your site currently is answering on port 80:
$ curl -X GET -I pandora.nlcv.bas.bg/.well-known/acme-challenge/xx
HTTP/1.1 307 Temporary Redirect
Server: nginx
Date: Sat, 19 Jan 2019 11:04:02 GMT
Content-Type: text/html
Content-Length: 180
Connection: keep-alive
Location: https://pandora.nlcv.bas.bg/.well-known/acme-challenge/xx
That is the sole requirement to use HTTP-01 validation. It doesn’t matter that you’re redirecting traffic to HTTPS, because Let’s Encrypt will follow the redirect to your secure port. Certbot’s nginx plugin will automatically configure nginx to respond to the challenge, on port 80.
Once you upgrade your Certbot and get rid of the duplicate certbot binary and libraries, HTTP validation should be completely seamless and automatic for you.
You do not seem like you need to do anything except fix your Certbot install.