@lukass2000 I run it as both a pi3b (primary dns) and proxmox container (secondary dns). Does your pihole have caching enabled? Responses from the pi should be much quicker once the pi grabs the...

I have setup pihole this exact way and it works fine for me. Try going to Settings > Services > DNS Proxy and input the pihole IP there. My guess is that maybe pihole is taking too long to respond so...