Hello,
I'm trying to create VLAN for guests. It's should be easy task, but on every tutorial I've watched the example was about only 1 ap.
I have WLAN 2,4GHz and WLAN 5GHz. I've also created already 2 virtual WLAN for my guests.

And my problem is how to create 1 VLAN with this 2 separate virtual WLAN. Should I create a bridge between this 2 WLAN? I really don't know.

Yes, create a bridge for your guest network. Add your guest IP and dhcp Server to that bridge. Then add your 2 vaps under bridge port. You will also need to add a firewall rule to block traffic between your networks.

Yes, sure. I know that, but I also want to create VLAN and I don't know how to put this step to advice above.