Hi 

4 The forced of Friedrich Hemmler also applies if he attacks an area where there are no defending units?

5 Temple of sigmar applies its effect also on the cards that do not have specific goals like troll vomit or judgment of verena?

6 Festering Nurglings  corrupt themselves, if there are no units in an area corresponding?

7 With Call for reserves I can pick up a unit and play immediately?  (the same unit)

8 This last question is a translation problem …

1.  Per the rule book page 11, quests are played in your quest zone.  Some newer quests have specific text that allows them to be played elsewhere.

2.  See Answer #1

3  The Blood Dragon Knight's action is triggered off of it becoming the attacker and declaring a zone to attack.  There is an action window just before Ambushes are triggered to allow for the Knight's action to happen before you are able to declare an ambush.  A similar situation exists for counterstrike, since that keyword requires the unit to be declared as a defender.  This happens after the window where the Blood Dragon Knight's action can happen.

4 Only if he is opposed in combat does his effect trigger.  If there isn't anyone to defend (or no defenders are declared) then his forced effect doesn't trigger.

5 If you are talking about Church of Sigmar (Not temple of sigmar) then only if the card targets a unit does the player have to pay extra resources.  Cards like troll vomit don't target units.

6 Correct they have to corrupt themselves if there isn't another creature

7 Yes you can replay the same card.  This is a common tactic with Rodrik's Raiders and their ilk.

8 The damage from shadow warriors is dealt to each opposing player, who then has the choice of which unit to assign the damage to. So in the case of a 2 player game your one opponent would have to assign one damage to one of his units in his battlefield.