Openvpn dns problem

I’ve problems running my my nordvpn (openvpn) client setup on my turris omnia router (turris OS 3.11.2). When I run it from one of my devices all is fine - also the DNS part of ipleak-net test. But not with running it on my router: it’s connecting fine to nordvpn but ipleaks-net shows DNS Leak: ‘DNS Address - 0 servers, 100 errors’. I followed this tutorial: (added the dns part in the wan interface of /etc/config/network), added dhcp-option DNS to the nordvpn config file, changed /etc/config/dhcp file to take the nordvpns DNS and I created a nordvpn config file (similar to /etc/resolver/dns_servers/99_google.conf) and tried this and the existing dns configs for knot resolver (as explained here: No success. Could anybody help me please?
Thanks in advance