Thanks for your looong comment. But at first I made a manual system, but it wasn't strong enough. So I opted for an script. The low speed is due to the spring, it is not powerfull, but I had to do it like this because otherwise, the system breaks.
I'll work on a new design, faster and stronger and maybe automatic.
By the way, I'll give you a tip : I looked to your scripts, and there were many, many "scene.addCircle ; scene.addCircle...". That's long and you can lose yourself in the scripts. So use the following script, it's way easier :
(e)=>{for(x, (i)=>{y})}
With x the number of things you want to spawn and y your script code.