I have the same problem. I tried everything possible, but there seems to be no way to kill NUNEZ without being attacked by CASTIGO.

To kill Nunez silently, first make sure all your mercs are out of sight from the natives, if they are seen by the natives when the shot is fired they turn hostile. Make sure you do it at night when it is dark, I usually succeed between 2-3 am. Use the silenced USP provided by Nunez and shoot him in the head a few yards away.

It might take a few re-loads, but it works eventually if you find the right spot to shoot from. Oh, and make sure there are no civvies around, I usually point my gun at them and they run away out of sight.

Snake Mission !
 

I'm stuck on a mission . I must kill chef of police in puerto viejo silently . I get a basket whit a sneake and i must lay it down on the floor in the room where i want my victim dead . It has a false bottom Hwo do i "activete" the baschet ?
Please , i need a quick answer !

In the room where the target is standing, second floor in the room with the desks, move the cursor over the desk closest to the door. Left-click and place the basket in that desk. Once that is done speed up time to let 5 mins or more pass and you'll eventually get a notice that the target is dead.

Thx for the quick answer , now i can continue playing this incredible game

Kill Mr. Sisters
 

Where can i find him , what shall i do ?

Mr. Sisters Lover ...
 

Where can i find this Dude , it says that he is somewhere in the safe zone ...

Mr Sister's lover, aka Elliot, can be found in Artrigo. Check the mini-map for his exact location. He'll need you to help him with something, so you need to travel to Santa-Maria after talking to him the first time.

Rescue Tanya
 

I'm stuck on the mission where I have to resuce tanya from el vertigo. I can intimidate my way past the guard at the gate, but once inside I cannot find tanya. Do I need to do the side mission for the archaeologist, or just kill all the guards?

No need to do the archaeologist mission if you have the right uniform and can bluff your way inside the prison through the front gate. Tanya should be in a cell on the second floor, the last cell on the left. She should also show on the mini-map as a blue dot. If she isn't there, which is very weird, I don't know what the issue is and how to help you.