It is possible to remove forwarding settings under the menu item Nameserver.
Click on the eye symbol next to the respective domain name.
You can remove entries with x:
A entry:
If you want to remove the forwarding of an IP address, remove the respective entry for type A.
URL-Forwarding:
If you want to remove the forwarding of an URL/Internet address, remove the respective entries for type URL.
CNAME:
If you want to remove the forwarding via CNAME, remove the respective entries for type CNAME.
Mailserver:
If you want to remove the forwarding to a Mailserver, remove the respective entries for type MX.