I think I have to kill borgie guard's on horse back well riding across the bridge and that's where I fail 50% of the mission, I just keep riding pass them to the end of the bridge, I think you have to kill at least 4 guards
I haven't figured out how to drew and use my sword well riding a horse 😵
You just select the sword from your inventory and press left mouse button, default attack button, while riding a horse to draw out your sword. Note: you probably can't draw your sword while galloping.