@OP
But you know that you should re-think that “One LAN” or Two routers with own Network.
Then, when you select this, we can say and help you with config.
For now, for teaching purpose read a Kirk PDF/MUM Video what is here: MiltiWan.
As always, RouterOS is not easy.. and even after years I still have what to learn about new feature what I never use… We love that 