I would love to take a look at it. I work until Sunday evening (I run a kids coding school) and then I'm on a little trip with my daughter. Mid-next week I'll have some time to connect with you on this.
Meanwhile, here's an example in Scratch: https://scratch.mit.edu/projects/794315773/
You can click see inside. The code is block-based, but basically works like pseudocode. Looking into Unity a bit, in your update loop, you'd want to multiply the RigidBody.Velocity by that 0.95 or whatever.