Mission: El Sin Nombre - 00:04
After regrouping with Alejandro he will give you a mask where you need to make your way to the penthouse. From where you are, walk forward past the swimming pool on your right until you get to a gate and an outdoor kitchen area. Once here, pickup the bottles and throwing knifes. Make your way through the gate and you will see a tree in the middle of the path, just after this there will be an outdoor balcony on your left. Climb the small wall to hump onto the outdoor balcony to get inside the building.
Once inside, go up the stairs and through the 2nd door in front of you. Once you've gone through the door you will see a
corridor that has a red light in it. Crouch walk down the corridor until you reach the end. Turn right and open the door into the next room. Whilst in the room, turn left and you will see an open window in the bathroom. From here, use the throwing knifes to takeout the enemy that’s on the stairs. After this, make your way to those stairs where the enemy was and jump upwards to the ledge.
From here, crouch walk into the room in front of you quickly. Once inside the next room, on your left you will see a painting that says “
Lazar Salgado 02/02/2019”. Walk further into the room and turn right and open the wardrobe to find the safe. Input
02-02-19 into the safe to open it. After opening the safe you can quit to main menu, no need to finish the mission.
Mission: Alone - 01:57
A little while into the level you will jump over a small wall and fall onto the ground below, yourself and Ghost will be discussing the rain. Turn right into the building and you will see a white car with a broken window next to it. Jump through the window and disarm the
shotgun trap. After this, go up the stairs and through the corridor. After opening the door, an injured NPC will be in front of you. Walk into the next room, don’t jump down to the floor below just yet. Turn left and go into the small room. Look at the calendar on the wall in front of you to find the safe code which is
10-10-80. The safe can be found just right of the calendar. Loot all the stuff from the safe and jump down into the next area.
Once you’ve dropped down, turn left and crouch walk to the door in front of you. Walk to the back of the right car and go through the next door. Crouch walk your way through the garage, in the 2nd half of the room you will find a laptop on your left with the safe combination which is
37-60-80. Go into the small room on your left to find the safe. Once the last safe has been opened, the achievement will unlock.
If you are still having trouble, feel free to use this video as a referece.
Hope this helped, thanks again.