Hi, I am making a fighting game and I am having trouble with the physics of the game. My problem is that my character has no force or ground friction, he just floats in the air. Is there any way to fix this problem?

You mean that your players levitate?
If yes, you need (for the beginning) simple gravity to keep your players on the ground.
Code:

---

 
function gravity
{
	while(me)
	{
		vec_set(temp, my.x);
		temp.z -=  500;
		trace_mode = IGNORE_ME + IGNORE_PASSABLE + IGNORE_SPRITES; 
		result = trace (my.x, temp);
		my.z -= result;
	wait(1);
	}
}
 

---