Apex Predator is the third mission in Hitman 3 set in Berlin, Germany. The mission takes place at a massive rave where Agent 47 must eliminate 5 ICA agents hunting him down. One of the most difficult challenges in the mission is finding and opening the safe in Rolf Hirschmuller's office.
Hitman 3 Apex Predator: How to Open Safe with Code
Before finding Hirschmuller's office, you first have to learn the code to the safe. To do this you must first obtain a Tech disguise and go into the rave. Walk through the crowd of people and to the right and you'll find a door with "Tech Only" written above it.
After going through the door you'll find two other Techs talking about robbing Hirschmuller. One of them states that the code to the safe is the same as the "year the wall went down." Given that Apex Predator takes place in Berlin, they are referring to the Berlin Wall, which went down in 1989.
After learning the code to the safe you can now move on to Hirschmuller's office. The office is heavily guarded and requires you to take out two bikers and find a keycard to enter. After obtaining the keycard in the next room head through the double doors by where the bikers were standing to reach the office.
There are more people inside Hirschmuller's office so you'll have to be wary while exploring it. To the left by some cabinets, you will find the safe. Punch 1-9-8-9 into the safe's keypad to find a gold idol and a brick of cocaine inside.
The idol can be used as a blunt weapon while the brick of cocaine can be used to achieve three different challenges in the Apex Predator mission. Achieving these challenges earns towards the player's mastery of the Berlin level.