I can't really provide any further guidance than I've provided already.
Your screenshots seem to match my remarks on where to find your router's options for configuring Pi-hole as your router's upstream (your WAN/Internet screen) or distribute it as local DNS server via DHCP (your LAN screen).
I cannot know how your specific router model would behave or what values it would consider valid for the numerous bells and whistles your router's UI allows to interact with.
You should consider your router's documentation and support channels to find out. Another approach would be to experiment with your settings and find out by trial and error.
That said, I'd probably begin with the preferred approach of distributing Pi-hole as local DNS via DHCP.
Note that clients would start picking up Pi-hole as DNS server only after their current lease time has expired and they'd renew their lease.
You may force a client device to renew its lease, e.g. by dis-and reconnecting its wifi network or by power-cycling the device.
There are routers that may not agree with setting a private IP address as DNS server, or those that would redirect DNS traffic to your ISP's servers, or those that always distribute themselves in addition to any DNS servers configured. Again, you'd have to consult your router's documentation and support for details.
Also, in order to better attract users from our community who have successfully weathered difficulties similar to yours, you could consider to include your router's make and model in your topic's title.