2 Routers , 2 Networks , Connect to each other

RouterOS Beginner Basics
1

I have managed to connect my office and home buildings with a cat6 cable.
Both office and home have separate internet connections and have their own LAN networks in different IP ranges.

At home, I have a MikroTik hEX RB750Gr3 doing the duties of providing internet to my home devices and computers. IP range is 192.168.1.x
In office, I have another MikroTik hEX RB750Gr3 doing the duties of providing internet to my office devices. IP range 192.168.2.x

Since I have both the buildings inter connected now, I would like to do these things

  1. Push backups from a computer in the office to home via the intranet.
  2. If the home internet fails, use the internet connectivity of the office at home
  3. If the office internet fails, use the internet connectivity of home at office.

I would like to maintain both the different networks in their own subnets.

Any ideas on how to get this thing done?