How to disable NAT?

Question

System administration

There are 2 MIKROTIK CRS125-24G-1S-2HND-IN switches connected to the router from the provider. (with his own firmware)
They do the job of a router and limit the speed. (Since you can’t do this on the router)
When configured as a router (factory), NAT is enabled
I don’t understand routing well yet, and as a rule I read websites or watch videos on YouTube, how different models are configured, in all cases people turn on NAT.
Disabling it or changing its actions causes the network to crash.
The problem is that the traffic goes through it and 2 switches cannot find each other.
The main question is: how to disable or bypass NAT?
In Google, I found similar cases, but my knowledge of the vocabulary on the sys-admin topic does not allow me to read it.
Could not, if not difficult, simplify what the person did in the following article:
https://forum.nag.ru/index.php?/topic/109599-mikro...
The answer is at the very end, the author himself solved the problem, but I didn't understand how.

The question is off topic, but who knows Mikrotik I will be grateful if you answer.

There is a routing sheet in which the paths are prescribed, who and where can be found.
In Mikrotik, similar actions are performed by IP>routes and similar by IP>addresses.
What role does IP>addresses play?

Are there any programs for network building training? (I saw that there is such a thing on Cisco, but maybe there is something simpler)
In order not to climb in a real device with connected computers.

Answer 1

When configured as a router (factory), NAT is enabled
and 2 switches cannot find each other.

Turn off NAT.

Answer 2

option 2: vpn network between two routers.