When my internet connection is cut off by a misconfigured VPN, immediately a window opens that says it cannot connect to the Internet. When I reconnect to the Internet the window loads elementary OS content. It looks like a elementary OS welcome-window or something like that. But it is not loaded in the browser. How can I disable this? I do not want any connection besides the programms I use! Please advise! Thanks!
This sounds like an issue with the Captive Portal Assistant. It's a tool installed by default to assist users in wifi networks with a separate login page (e.g. in a hotel). Most likely it (wrongfully) recognizes your connection as "captive network" and tries to assist you (which doesn't work of course, as there is no login page to show). After successful login, it normally displays
elementary.io to test the connectivity.
If you don't want this functionality, you can remove the package
capnet-assist. That being said, elementary OS does not track you in any way. The source code for
elementary.io is even open source, so you could check it and make sure it does not track you.