How to set up 2 routers in different networks?

Question

Network routing

Hello everyone,
There is an ADSL modem ZTE ZXHN H208N, which has Internet, Asus Lyra is connected to it via cable -> Lan-Lan or Lan-Wan, I can’t say for sure, because there is no specifically dedicated Wan port on Lyra.

There is a static, white, Ip address for access from the outside, and there is a DVR with cameras connected to the router, with port forwarding to this static white address.

Previously, with the settings on one ZTE, everything worked. Access to cameras via the Internet and within the local network, but with Wi-Fi everything was bad. Now there are 2 Asus Lyra connected to each other via WiFi, but the cameras do not work.

The question is:
Given
1) ZTE modem with subnet 192.168.1.1, with WiFi turned off and port forwarding configured Remote Host -> 192.168.1.2.
2) 2 Asus Lyra goodies, with WiFi enabled, configured subnet 192.168.2.1, configured DHCP from 192.168.2.11-192.168.2.200, configured port forwarding to 192.168.2.2
3) DVR with ip address 192.168.2.2 and 8 cameras in a row from 192.168 .2.3 to 192.168.2.10

Internet and Wi-Fi network is working properly, LAN network is constantly having problems, so the DVR is probably not available, and WAN IP is generally 192.168.1.2 on Lyra.
Moreover, the network and the Internet and the DVR work fine immediately after rebooting Lyra and until an indefinite moment of failure

. How to make all this balalaika play correctly? It is necessary that the entire network be managed on Lyra, and ZTE should simply be a gateway for the Internet.

Thank you and sorry for the crazy description

Answer 1

modem in bridge mode and configure wifi routers