How to repair bent scissors?
It is normal for scissors to have a gap between the blades when they are closed. The blades are bent on a slight curve so that there is a minimal point of contact between the two cutting edges while a closing cutting action is taking place. Without this there would be terrible cutting performance due to tolerance in the surface flatness of the blades and of the ground cutting edges. 

Note that you do not want to be heating up the scissor blades to soften the metal enough for trying to hammer on the blades. Doing this will take away the hardness of the blades and basically ruin your scissors. The softened and untempered blades will not hold a decent cutting edge. I suggest that if you try this the scissors will rapidly loose their status as your favorites.