Do medics only fix troopers or all ships? Do they do it automatically?
They fix any non-mechanical unit. And if they are close enough, they heal them automatically.
Then who fixs mechanical units?
workers fix mechanical units
Do shields fix units or just give them 2x hp? Do all units get fixed/protected by shields?
Shields only give them X2 HP's. And yes, everyting under shields gets protected.
P.S. Did you get the PM I sent you, protoss?