Block public DNS like google and other malware dns

In Parental Control -

Block Bypass Methods

Prevent or hinder the use of methods that can help bypass NextDNS filtering on the network. This includes VPNs, proxies, Tor-related software and encrypted DNS providers.

But I think you chose the worst solution adding only the IPv4  DNS if I see it right and you might have leaks on IPv6.

Look at Setup - Setup Guide - Select iOS and read.

I don't know how it is on iOS or what version you have but if you can, use DNS-over-HTTPS or DNS-over-TLS

As mentioned by others in this thread, I also see those leaks from time to time on several leaktest pages with either the app or the profile. Everything is set up correctly.

You said you are using the app. Is it enabled and configured like it says in Setup guide?

All you showed was this,

https://help.nextdns.io/media/download/80kvnn/FC42C30E-5A8D-41F3-8080-38347BC106EC.png

Google can't magically enter your phone.
Even on Android I can block anything from Google. With a firewall you can monitor all the connections.