I am trying to make a top down 2d soccer game.
I have 2 sprites on the 'pitch' and have the following code which works out a curved path (as if the ball had spin on it) for the ball to travel from Player 1 to Player 2:

I have also declared another Curve which I want to use as the speed the ball travels at:
export(Curve) var landing_curve

I want the ball to traverse the curve dictated by the curve above. I have done this via this code:

The snippet above works to move the ball but the speed is not correct because it is not applying that which I have dictated in as 'landing_curve'. I have tried a number of methods, including trying to use a landedness value
export (float, 0, 1, 0.01) var landedness
which I saw in some video, and trying to interpolate my Curve to then exchange t for in the last line but I can't get it correct.
How can I write this code so my ball travels at the speed dictated by landed_curve?
I have attached my full script if that helps and this is a video of what I have so far:
https://youtu.be/BtkG-_k-UMw