I need to set 2 bridges: one with 4 ethernet ports (for servers) and one with 6 ethernet ports (for wireless access points).

In my wireless bridge I intend to setup a hotspot and on bridge for server I need to leave it out of hotspot.

Now I have a single bridge. My curent config is like this: on ethernet1 I have internet connection (86.127.70.132) and on bridge (who have connected all other ethernets) I have gateway for my public class (80.97.140.1/24).

If I make another bridge, what IP should I set on that? It will work to set same 80.97.140.1/24 too?

No. You will need to subnet the network.

Ok fewi, but I'm very beginner on subneting... and mikrotik also.

I need IPs from 1 to 20 on servers bridge and IPs from 21 to 255 on hotspot bridge. How should I do that?