You just need to connect the raspberry to your network, set a static IP and set the DNS server in your router to the IP of the RPi. Your router handles all the Routing and Wifi and the RPi just resolves DNS queries.
I suggest looking up what DNS is and that should clear things up for you.
Btw, I gess you meant wlan with wan, those are two different things in networking.
You should just put it next to your router with a wired connection. This should improve latency for dns requests and give you less headache because no problems with wifi can happen.
1TB (nvme or ssd) on all my notebooks
2TB (nvme) on my desktop
150TB (hdd) on my server