Just after Potsdam in August 1945, could French, British, and American military and diplomatic personnel move freely through the Soviet zone of Berlin, and vice-versa? What were the borders between the East and West zones like at that early time?

Also, what were the primary functions of the American forces in the city at that time? Was the focus more on re-establishing government services for the populace, cleaning up the devastation and rebuilding, ensuring that no lingering German resistance remained, or securing the zone from the Soviets? (I know it was probably all-of-the-above, but I imagine one goal tended to dominate the others in terms of how much time and energy they were putting into it.) Thanks!