How would you configure this?

I would like to create a guest-wlan network (192.168.50.0/24) which is completely isolated from the rest of my network.
So far i managed to create a virtual WLAN and a DHCP server on the Mikrotik AP.
However i don’t know how to “tunnel” the traffic from the guest network to the network which is connected to my VDSL modem.
Please find attached a schematic of my network setup. (All APs are Mikrotik devices)
How would you solf this “tunneling” or is there a simpler way (since i am not an expert)?
Network.jpg

USE VLANS to separate traffic subnets.
Then at the router ensure vlan-guestwifi has access to the internet (WAN) but no connectivity to the LAN.

I guess the VLAN is optional since blocking acces to other network segments in the firewall of router 192.168.50.1 is already sufficient?