If the command above works correctly, you should be setup for autorenewal. You can then easily test your renewal with: certbot renew --cert-name www.wavi.at
Hello @erich.wanker and @griffin
My take on the OP is asking for auto renew information. Cert is already in place and valid until January 5, 2021.
As far as the auto renew question...
The Certbot installation on your system comes with a pre-installed Scheduled Task that will renew your certificates automatically before they expire. You will not need to run Certbot again, unless you change your configuration. You can test automatic renewal for your certificates by running the command
Appreciate the thought, but @erich.wanker set himself up for disaster by using --standalone without specifying hooks to stop and start apache. Adding those hooks would still be not be good because it would unnecessarily complicate the process.
The command I had you run with --apache will acquire another new certificate for you. The reason I had you run that command was to update the renewal configuration for your certificate so that you don't run into trouble with --standalone. @Rip made a good point about testing your renewal.
Use the following command if you want to test your renewal: certbot renew --cert-name www.wavi.at --dry-run
Use the following command if you want to manually renew (without hurting your autorenewal): certbot renew --cert-name www.wavi.at
I'm just amazed that Erich managed to go this more complicated route right at the beginning and succeed. Most who are new to certbot would not have had the foresight to actually stop apache and many if not most would forget to start apache afterwards. Bravo for @erich.wanker for a thorough beginning!