Density & Friction

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I'm making a zombie game so when the actor and or zombie collides they move. Like if I would hit the zombie actor it would move back and if the zombie actor would hit me I would move back. How would I completely stop this? (I want them to collide but when they do I don't want anything to move and I don't the person to be able to push an actor away or the zombie to push me away) I've been playing around with the Density and Friction of both actors for like about 45 minutes now with no luck. I Can't unchecked movable because well nothing will move. & I set Bounciness to 0. I tried setting Density to 3000 and friction to 10 and a bunch more stuff. Could someone help me with this?

Thanks in advance