I would like to use ISP2 instead of ISP1 internet from PC1 computer. But I'm not even able to ping antenna A, however, antenna B shows that it is connected to antenna A. I would also like to access all devices on 192.168.1.x subnet and vice versa. What I'am missing?
Your devices do not know that the other subnet is directly bridged. For example, PC 1's address & netmask tell it that only 192.168.0.x is on-link – anything else is to be sent towards the gateway. Then the exact same thing happens on both routers C and B. (Eventually the packet is sent to ISP1 and discarded there.)
There are several ways to connect the two subnets:
One large subnet
If you change all netmasks to /23 (i.e. 255.255.254.0), you will end up with all devices being in one subnet and they'll know that they can reach each other without using a gateway.
When doing this, you should enable the WDS Bridge option, since it preserves MAC addresses through the bridge. (Standard Wi-Fi cannot do that, so without the WDS option the entire network B will appear to have a single MAC address when looking from network A.)
You can keep the netmasks as-is, and give certain devices IP addresses from both networks – for example, PC1 can be 192.168.0.1/24 and 192.168.1.1/24 at the same time. (Unfortunately on Windows this is only possible with static configuration, not with DHCP.)
Instead of transparent bridging, switch one of the antennas for 'router' mode. (Do not activate NAT – just routing.) Configure it with an 192.168.0.x address on one side and 192.168.1.x on the other.
Then configure router A to have a static route for 192.168.0.0/24 via the antenna's 192.168.1.x address, and do the exact opposite on router C.
(Note this doesn't need to be done on the antennas, it could be handled by a separate router as well. For example, Router C itself might be capable of this, as long as the OpenWRT doesn't insist on "LAN vs WAN" and just lets you configure two coequal networks.)