Walking Problem - Arms pinching torso - Pants stretching each other

[Justastudent]

Hello,

I am still learning the program.

The torso and all the limbs are in different layers. 

When the arms move the torso is pinched to the side. Why is that? Can I change that the torso is not dependent on the arm movements?

And why does it look like my pants are one stretchy mess when I have two separate layers for Left Leg and Right Leg? How can I make them not stretch each other.