Good day I want to route my steam connection to my 2nd gateway
/ip firewall mangle
add action=mark-connection chain=prerouting comment=Steam dst-port=27000-27060 new-connection-mark=steam protocol=udp passthrough=yes
add action=mark-routing connection-mark=steam new-routing-mark=GW2 passtrough=no
/ip route
add gateway=ether2 routing-mark=GW2
I just can’t make it work. 
Do you really meant “dst-port=27000-2760” and not instead “dst-port=27000-27600”?
If this was a typo, it might be part of the problem.
that was a type sorry fixed it. anyhow steam connection still wont go to 2nd gateway
As UDP is stateless, you can’t use mark-connection - there is no connection to mark.
try
/ip firewall mangle
add action=mark-routing chain=preprouting comment=Steam dst-port=27000-27600 protocol=udp passthrough=no new-routing-mark=GW2
UDP protocol is stateless per se, you’re right.
But ROS conntrack keeps state of UDP connections by its own, you can mark-connections on UDP.
Post a screenshot where counters can be seen. Is that router masquerading correctly (if it needs to)?. Post a diagram with rest of devices, IPs and routes.