Serious help with setting up Pi-Hole

I have watched multiple videos on YouTube, looked through everything I can find on here, as well as Google’d like you wouldn’t believe. I am currently trying to set up Pi-Hole on a spare Raspberry Pi I have laying around and am running into issues.
First off, below is the list of hardware/software I am using:
Router: Turris Omnia
Raspberry Pi 3
NordVPN
Windows 10

I was having trouble with my devices using the DNS Server of my Raspberry Pi. In NordVPN I turned off “CyberSec” which added my Pi IP to the top of the DNS Server list, but there are still two NordVPN servers after. The only results I am getting in the web interface for Pi-Hole are from localhost (~700 results so far). Also when I was searching for an answer before making a new post I saw this post. When I do an ‘nslookup’ on pi.hole I get the following result:

DNS request timed out.
timeout was 2 seconds.
Server: UnKnown
Address: 192.168.1.101
DNS request timed out.
timeout was 2 seconds.
DNS request timed out.
timeout was 2 seconds.
DNS request timed out.
timeout was 2 seconds.
DNS request timed out.
timeout was 2 seconds.
*** Request to UnKnown timed-out

In my Router settings I followed this (it’s in Czech but you can easily use Google Translate.
That’s what I did) guide and watched this video on how to set it up. I only followed the last part “Pi-hole and WAN”. The beginning is about putting it directly on my router which I did NOT do. It is on a Raspberry Pi. After closing NordVPN and going into Command Prompt > ipconfig /flushdns > ipconfig /renew > ipconfig /all > my router IP (192.168.1.1) is what shows up for DNS servers? Once I start NordVPN again and redo all the stuff I just did the Pi shows up with the 2 NordVPN DNS servers after it. In the NordVPN settings I added the Pi as a custom DNS server but why wouldn’t it show up anyway? I also found this post which I followed. None of this has worked so far. Is there a place I could get a step-by-step guide? I am willing to do it through and LXC but I just have a Pi laying around I would like to use. Either way if I could get step-by-step instructions. If it matters I have an Asus RT-AC68U set up as an AP on my network. My Omnia is 192.168.1.1 though.