It produced this output: Saving debug log to /var/log/letsencrypt/letsencrypt.log
Obtaining a new certificate
Performing the following challenges:
http-01 challenge for pi-g48-1og.spdns.de
Using the webroot path /var/www/html for all unmatched domains.
Waiting for verification…
Cleaning up challenges
Failed authorization procedure. pi-g48-1og.spdns.de (http-01): urn:acme:error:connection :: The server could not connect to the client to verify the domain :: Fetching http://pi-g48-1og.spdns.de/.well-known/acme-challenge/kDQZkWpV0yuiiGmjJABgHM-g1W5MuoBmsbm2UtlNIAk: Timeout during connect (likely firewall problem)
To fix these errors, please make sure that your domain name was
entered correctly and the DNS A record(s) for that domain
contain(s) the right IP address. Additionally, please check that
your computer has a publicly routable IP address and that no
firewalls are preventing the server from communicating with the
client. If you’re using the webroot plugin, you should also verify
that you are serving files from the webroot path you provided.
My web server is (include version): nginx 1.10.3
The operating system my web server runs on is (include version): 1.2 2018-11-13-raspbian-stretch-lite
I can login to a root shell on my machine (yes or no, or I don’t know): yes
I’m using a control panel to manage my site (no, or provide the name and version of the control panel): no
I am trying since 2 days, but i don’t know what to do.