A few questions about Self Defense and home defense laws for Law Enforcement or people in the legal community.

In view of recent event I was wondering the basic law of PA for home defense and conceal carry. Two example standout in my mind.

Situation 1;

In my house at night hear some sound go downs stair and see a intruder.

What course of action can I legally take?

Situation 2:

I am on the street and a person try to rob or try do do boldly harm to me by physic force, knife, or gun.

What action can I take?

I have read PA law and it does not seem so cut and dry.

Any input would be appreciated.

Thanks, Nick.