Hey @samurai_fish! Welcome to the forums!
You need to increase the player’s MAX speed, you’re probably topping out.
You can right click out in the open and use “Get Character Movement” and then from that use “Get Max Walk Speed” and “Set Max Walk Speed” and then replace your “Get Run Speed” and “Set Run Speed” variable with that.
It is set by default to 600 (cm/s) or 6.0 (m/s). When you stop, you can then “Set Max Walk Speed” back to the default of whatever you want it to be. 
Hope that helps!