Hello
Navigation within any page requires the use of IDs which is the part of the URL after the # symbol (
https://www.w3schools.com/html/html_id.asp). Is this the part you wish to change? To do so you can create your own ID tag with the following within any custom module or indeed add them to your templates index.php (../templates/[YourTemplate]/index.php)...
<div id="about"></div>
To link to this ID you would have the following...
http://parkettleger-augsburg.de/#about.
Ciaran