Welcome to the Pi-hole community, Jubran_Makhouly. 
Pi-hole requires to be accessible by a stable IP address, which does not seem to be the case for IPv6 from your debug log:
*** [ DIAGNOSING ]: Name resolution (IPv6) using a random blocked domain and a known ad-serving domain
[✓] 08.185.87.110.liveadvert.com is :: via localhost (::1)
[✗] Failed to resolve 08.185.87.110.liveadvert.com via Pi-hole (2003:<redacted>)
[✓] doubleclick.com is 2a00:1450:4001:808::200e via a remote, public DNS server (2001:4860:4860::8888)
Consider using a stable ULA address instead, see Use IPv6 ULA addresses for Pi-hole.
Your debug log shows a ULA already being available on your network.
In addition, you have connected your RPi via WiFi (wlan0) right now.
If your RPi is equipped with both WiFi and LAN, consider connecting via LAN (eth0) instead. A LAN connection is more reliable than a WiFi one and offers better latency as well.
You can find out about the current address by running the following command on your Pi-hole machine:
ip -6 address show
Look for addresses starting with your fd67:.. ULA, note down the one for your preferred interface (wlan0 or eth0), and then reconfigure your Pi-hole by running:
pihole -r
and choose Reconfigure.
As you are new to RPi and Pi-hole, it might be a good idea to switch off IPv6 in your router altogether, run Pi-hole with IPv4 for a while and get familiar with it.
You can always switch it back on after you have familarised yourself with Pi-hole and did a bit of background research on IPv6, which comes with its own problems and limitations.