Ideal setup guide with ISP Router + Openwrt (rpi4) + WiFi -AP

I have a strange question regarding DHCP server on Rpi4(Openwrt installed)
I am connecting Telekom router + rpi4(openwrt)+ Xiaomi Ax3600(as Access-Point for WiFi)
What I want to ask is how should I setup the DHCP server so that I have 0 issues in blocking ads and also in terms of IP address conflict.
How should I proceed further? I mean should I setup static dns Address in my Router and let rpi4 manage DHCP server and the Xiaomi Ax3600 in AP-Mode?

Is this setup correct? If so how can I do the DHCP setting in openwrt??? Can I switch off the DHCP server on Telekom router? Will it work if I do so?

Hoping to get a reply soon.

I also have an idea of print my ISP router in pure modem function (bridging mode). If I do so, will my rpi4(with IP Address) continue to work without failure and will it act as DHCP server?

If yes, please guide me where to find a guide to do it. I searched online for long, but couldn't find a perfect solution for my problem.

Thanks in advance

Sorry, I have not understood your requirements, I will write common considerations.

Router creates NAT, so additional LAN network with virtual IP addresses exists.

In your case you should decide, what to do:

  1. RPi is 'second' router, creating additional LAN (DHCP server on it works).
  2. RPi is dumb AP, so it just connects interfaces via bridge (No DHCP, no routing).

Thanks for your time, i didnt know myself on how to frame this Question to ask my Problem.
According to your suggestion i wanted to have the 1st Setup.

That means i want my RPi to do the DHCP Server function of assigning IP Address to all the Devices. that means i dont want to have 2 DHCP Servers running for the single Internet to block ads and stop malicious attackes.

I want to know can i create my own IP Address with DHCP Function on Rpi ? if yes how ?
if i leave the default router setting on my ISP Router, it also has its own DHCP server. That is what i mean to switch off and get this function only from Rpi. by the way i dont want the WiFi capability of Rpi. For this purpose i have Xiaomi AX3600 as WiFi in AP-Mode setup....

ISP-Router - > Rpi(DHCP-Server) ->>XiaomiAX3600(as WiFi-Router in AP-Mode).

i hope i have made my situation and problems little bit clear. All i am concerned is about blocking ads if 2 DHCP Servers kept running on a single Network, then the Adblocking Function will not be 100% effective... Thats my only concern...

Hoping for a reply.

It is worth stating that DHCP does not have anything to do with Adblock. Typically, ad-blocking is done with DNS, which is a separate function. Your DHCP server will simply advertise what DNS servers are desired for the client devices to use.

Thanks for your reply. Till now I was under the impression that only one ip address series in a network needed to block the ads 100%

I also want to know how I can change the ip address of rpi4? And subsequent Device IPs?