Multiple bridges are a bad idea, see https://help.mikrotik.com/docs/display/ROS/Layer2+misconfiguration as to why, and http://forum.mikrotik.com/t/using-routeros-to-vlan-your-network/126489/1 for a primer on VLANs on a Mikrotik
Multiple bridges are a bad idea, see https://help.mikrotik.com/docs/display/ROS/Layer2+misconfiguration as to why, and http://forum.mikrotik.com/t/using-routeros-to-vlan-your-network/126489/1 for a primer on VLANs on a Mikrotik