I'm just going to refer you to @AceCalhoon's answer - I can't really add to it.
You can also take the Counterspell by the NPC as a win - they've used up their reaction and at least a 3rd level spell slot.
You can Counterspell a Counterspell ...
Assuming you still have your reaction available.
Reactions reset at the start of your turn so this will usually be the case. However, if you have Readied the spell then that uses your Reaction.
... but not if your original spell was a Bonus Action spell
The reason is that spells cast with bonus actions have this limitation:
You can't cast another spell during the same turn, except for a cantrip with a casting time of 1 action.
Counterspell a) is not a cantrip and b) has a casting time of 1 Reaction. So, if you cast a bonus action spell; Counterspell is not available to you.
This is something to bear in mind before your Sorcerer Quickens that spell.