I need quick help. How to I make it so that when I hit the "part" it flings in the opposite direction

I’m trying to make it so that when the player touches the part, it flings in the opposite direction like a soccer ball or a hockey puck.

You should calculate the direction to the player from the part by taking away one’s position from the other.
Then you can (iirc) multiply the vector by -1 to oppose it’s original direction.
Finally, you can replace the Y vector with whatever value you wish to use, and apply a force in that final direction using preferred methods.