Discourse requires ports 80 and 443. It cannot be run on a nonstandard port.
You will need to disable or remove Apache to use ./discourse-setup.
If you want a reverse proxy in front, you can see How to set up Discourse on a server with existing Apache sites, but it requires a pretty good understanding of Apache and what reverse proxies are (and maybe English!). Oh, or the URL in the message that you include above.
You can copy samples/standalone.yml to containers/app.yml.
I have a German last name but speak no German outside of a couple dozen words all having to do with beer.