Hello,

I recently got my mikrotik as a real device as i am studying networking in my school and got 2 mikrotiks hap ac both on long term version and 2 ISPs and my goal is to have both mikrotiks accessible on same subnet (192.168.0.0/24) and when ISP1 goes down, all traffic will get redirected to backup mikrotik with ISP2 and as soon as ISP1 works again i want it to switch back from backup mikrotik to main one again because ISP2 has a data cap.

Network diagram is included below.

Thanks for help.

Okay so you are not proposing a backup router,
but a backup such that at least one ISP is available at all times on the LAN, if one goes down.
Well you dont need two routers for that, one will suffice!
It all depends on how you setup your routing for the most part.

Attach both ISP modems to the primary router (use the second hapac as a switch/AP for example).

What would a more interesting exercise is how to have a backup router in case the primary router fails (assume dead dead dead)
Thus you would need a managed switch (even just basic port translation)
such that both ISP connections go into the switch (lets say port1 and port2, Port1 is connected to ports 3,4 and Port 2 is connected to ports 5,6
Thus hapac one is connected to switch ports 3 and 5
Thus hapac two is connected to switch ports 4 and 6.

That way both routers have access to both ISPs full time.
Then you will need one connection dedicated I think, between the two routers.
The functionality in the router that applies is VRRP.