How to add a domain or path for inner pages of website? [duplicate]

Im not an website developer, and totally beginner. And that's why im asking this question: Lets say my Webpage is hosted on https://www.google.de . And my Webpage has inner pages for example for Contact . So when now im deploying my webpage the link for Contact is like this https://Desktop/user/project/Webpage/Contact.php

This looks dreadful . So what can I do instead that my Contact link looks like this https://www.google.de/Contact

Hope anyone can help and tell me what to do .

Info : Dont know if its help but my Webpage is hosted with Firebase and I get the domain from Ions