Cname for OpenCart

i am using DirectAmin and opencart 2.3.0.2.
made a CNAME so i can ensure that a certain domain lands on another site, whereby that other site is shown but the domain name remains in the bar.

See for example https://debesteingifts.pixelplus.nl/
You can ignore the security message, because there is no SSL active on that subdomain.

But you can actually see that this loads "debesteingifts.nl", but in the URL bar it always stays "debesteingifts.pixelplus.nl".

If i click on something site go back to the real site,(i think OpenCart forces this).
For example, if you go to contact page you
it display in doaimbar
https://www.debesteingifts.nl/index.php ... on/contact
instead of
https://debesteingifts.pixelplus.nl/ind ... on/contact

who can help me ?

TNX a lot