I would like to now how to put a moving kill ball smoothly on my map. I know about the physics to normal and the path it follows, but I dont underatand how to make it travel over a flat surface. Please help
Well if you want it to travel on a smooth surface you'd have to spawn it on top of a man-cannon so that it shoots across your map. Otherwise, you can spawn it on a slope I believe so it rolls down the hill.
I know how to make it woth a man cannon, what I cannot figure out is how to make it travel in a straight path on a flat surface even with the rest of the map
It's a ball - it has physics pretty much like a real ball. You need some kind of pushing force to get it rolling, and then it will roll straight across level ground until it runs out of momentum. Unfortunately the forces that will act on it are limited - weapons (e.g. concussion rifle, grav hammer) if you want the players to do it, or man cannon/grav lift. I'm assuming you want it to happen automatically. If so, it has to be the latter. You can rotate it so the stream is parallel to the ground - that's about all I can advise. That's probably easiest with a grav lift, since you can set rotation lock to 90 degrees and just rotate it one turn.