@stefan-franz actually preparing a system to be a safe and well running web server is nothing that can be achieved by a simple tutorial, let alone to maintain it and keeping it safe.
If you don’t have the experience and knowledge, I recommend using Plesk or similar management console. There the groups and users and security features are on a better level for public web hosting.
Although I have years of experience with Linux ans web servers I wouldn’t dare to maintain it myself - unless I was a administrator fulltime.