Good day!
I can help You with your MikroTik routers confidently and quickly because I am MikroTik certified network engineer (MTCIPv6E/MTCTCE/MTCNA) having over 10 years of experience in configuring, maintaining and troubleshooting of enterprise MikroTik devices (access points, switches, and routers).
You need to use mangle to mark connections and forward them to the right WAN.