i just escaped the fire and sam is on the walkway outside. i dont know what to do to get to the next part. he cant touch the street and i cant kill civilians...where do i go from here?

Follow the walkway around to the right and then the left until you see an opening in the railing. There you can jump across to the next building's walkway and proceed from there.

And make sure the civilian randomly patrolling below doesn't see you. He's hard to keep an eye on.