Localhost and remote access suddenly stopped working

[Plunjukl]

For some time I've been using XAMPP to test my website with localhost which worked perfectly. Yesterday I opened my root directory for outside connections by editing some files in apache according to some explanations I saw on the internet, opening a port and disabling my firewall. This worked fine as my localhost still functioned and others could also access my website. Today my computer is suddenly unable to use localhost and the access from other computers isn't possible as well. If I type my IP I get the usual "It works" but if I try to access anything else this way It fails, and it also fails when I type this IP on another computer, unlike yesterday. Does anyone know what could have gone wrong all of a sudden?

[Altrea]

=> [INFO] How to not fail getting help here (Section "Scope of support")

Evaluate if your topic is in scope of support of our board. We don't want to provide...
...support for live, production or public accessible environments.
XAMPP is not configurated for such environments (default passwords, many activated and probably unnecessary modules, not tweaked for performance, scalability, stability or security). This board does have several entrys about hacked XAMPP installations because of using unprotected XAMPP installations in not supported environments. XAMPP don't want to fit every possible use case and there are other (also free) alternatives for such environments.