Nav menu links change on every page

I have two pages: https://www.miquelsl.com and https://www.miquelsl.com/index.php/aviso-legal.

Both pages use the same Nav Menu (main).

The Nav Menu items link to:

– miquelsl.com/#acercade
– miquelsl.com/#servicios
– miquelsl.com/#galeria
– miquelsl.com/#contacto

However, when I go to the other page I created https://www.miquelsl.com/index.php/aviso-legal then the very same Nav Menu links automatically change to:

– https://www.miquelsl.com/index.php/aviso-legal/#acercade
– https://www.miquelsl.com/index.php/aviso-legal/#servicios
– https://www.miquelsl.com/index.php/aviso-legal/#galeria
– https://www.miquelsl.com/index.php/aviso-legal/#contacto

And I don’t understand why they do this, as I want them to remain just the same as on the homepage https://www.miquelsl.com, I do not want to use different Nav Menu links.

Please let me know?

Thanks!

The page I need help with: [log in to see the link]