Two routers on the same network, how to set it up correctly?

Question

Computer networks

At the moment, all devices are powered by a router from the first apartment, I live in the second ...
Ideally (except for increasing the signal), I would like to organize a local network inside the second apartment, independent of the first. If I'm not mistaken, there are two ways:
1) connect lan1 of the first router to the wan of the second one and configure ....
2) connect lan1 of the first router to lan1 of the second router ... (I'm not sure if this is correct, I'm more inclined towards the first option)
In general, I have never encountered this and how to do it right is not yet clear to me, and what to do with the DHCP server of the second router (not all devices support manual configuration), whether DHCP will slow down the connection inside the second square. ?

...
upd: issue resolved
upd:2works, but not as fast as we would like ...
Cable length (cordex cca utp 5e, not the best solution) turned out to be 25 meters

Answer 1

1. You can make NAT: plug wan of the second router into the lan of the first one. The second apartment will have its own LAN, DHCP and full-fledged Internet. The setup is very simple: set the ip on the second router so that the subnet does not coincide with the 1st apartment.
For example:
in the 1st apartment, the network is 192.168.1.1/24
in the 2nd apartment, the network is 192.168.2.1/24
In the second apartment, problems with access from the outside may begin, but if the devices support uPNP, there will be no problems (and almost all modern devices support).
2. You can combine apartments into one local area. All devices in both apartments will be on the same subnet, see each other, receive DHCP from router 1. To do this, the second router must work as a hub.

Answer 2

I have a similar problem but with a different reason. WI-fi does not break through the wall between the kitchen and the room, and I had to buy another router. But there is also a system unit on which all sorts of junk lies, to which you also have to constantly climb.
Netgear 614 and 1000 routers.
The scheme is
Internet - 614 (192.168.1.1 255.255.255.192) - 1000 (192.168.2.1 255.255.255.0) - a system manager is plugged into it with a ball (192.168.2.2) The
Internet works, but when connected to a network drive via wi-fi to the first router, the system manager with a ball in a different subnet is not visible.
DHCP is enabled on both routers.
I tried to restrict DHCP on the first one and turn it off on the second one (to make a hub out of it). But I can't find a range of addresses. It swears at my options (invalid ip adress/ip address is conflicted with wan ip subnet).
Can someone tell me the cherished combination?
Thanks in advance.