As you use a router as a AP you will end up double-NATing.
The wifi router assign the IP, and the WAN for him is the second non-wifi router.
I suggest a true AP, or maybe your router allow to switch to AP mode. That way the AP just serve the purpose to add WiFi to your first router.
If you want roaming between AP, if a device travel to another AP zone, and the device don’t loose the connection and it connect to the second access point, you need AP that are designed for that, like unifi/aruba/cisco got controller for that purpose