How to relay one modem router to an other ?

So I have modem routers A and B.

I want to connect the two routers via a LAN cable.

The internet connection (VDSL annex A) goes to router A.

I want my computer to use the WiFi of router B and be able to access the internet.

Router A is a Speedport plus

Router B is a Draytek 2762 AC.

Good news is that I can access the control panel of each modemrouter by using the IPs I mentioned above, bad news I cant connect to the wifi of router B

My fruitless attempts thus far:

1) I set router A getaway as 192.168.1.1 and router B as 192.168.1.10

2) I disabled DHCP on router B

I try to connect to wifi of router B thinking that I will be able to connect to the internet but it doesnt even connect (actually it immediately disconnects after it connects, wifi works though I tested router B with DHCP enabled and it works)

I saw an option on router B (DHCP Relay Agent) it has a field to enter an IP.

I put the getaway of router A there (192.168.1.1) but It does not enable the option I click on "ok" and nothing happens (normally when I change a lan setting after clicking ok router B restarts)

So what am I missing? :P