Hooray. This is officialy a 'wet job': targeted assasinations. Lovely.
First you knock off the lady's boyfriend, then you nick her gold from the coffer at the footend of her bed. You don't really feel like a gentleman now, do you?

There is a small locked door in the 'L' shaped alley between the two first streets. Break the lock open as quiet as you can, and creep into the apothek's back room.
The name of the apothecary reminds me of something... ;)

Open the apothek front door quietly. At the opposite end of the street, there is a window with a sniper. Shoot him before he spots you, then use the drainpipe to climb up to his room.

One of your targets is at his desk, right inside the door. After you honored his contract, destroy the picture behind the desk; it hides a switch. Activate it, and a secret door opens across the room.

Another interesting wine cellar. The stopper in one of the barrels stick a bit out. Poke it, and a secret passage opens in the wall to the left of the barrel.
There is an alternative path out - it becomes obvious when the gold is found.