The Jacuzzi job is one of the hardest missions if you have no good idea how to do it unseen, but it is possible. This time, watching the video might be a better choice than these descriptions.
There are three options:
(1)Go to to the balcony on the right side of the map, climb over the wall and wait until the secretary starts walking towards the safe. Go into the room and walk towards the door on the left (you don't have to sneak, the secretary will only notice you if you run) to the room where the fuses are and destroy them. Then run back to the previous room and take the money from the safe. Or (2) sedate the secretary once she opens the safe and take the money.
If following (2), take out the fuses now and run into the main room to take the statue. (one and two now converse again) Run towards the left door to the corridor. You will run into one of the male guards, so just sneak pass him, he won't notice you in the dark if you're stealthy. Run to Charlie Sidjan's room and shoot him in the head with a silenced gun. If there are any women in the tub they'll notice this, if they are in their bathroom they won't. However, they always seem to make their way to the tub if you run to Charlie's room and you won't make it if you don't, so this might be difficult. Don't get too close to the jacuzzi before shooting, otherwise the male guard will notice you.
After the hit run to the elevator and wait for the technician to arrive. When he does, go into the elevator and leave the penthouse.
(3) Enter the door right in front of you when the mission starts and hide behind the table. Even when you don't crouch, neither of the guards will notice you. Once they both passed by, run to Charlie's room and hide behind the screen between the door and the tub. Wait for the women to go to the bathroom and strangle Charlie with the fiber wire. Drag his body behind the heart-shaped bed and try to get behind the door before the women come back in (close call). If not, try hiding behind the bed. They won't be bothered by Charlie's absence.
Go to the fuses and once the secretary opens the safe, break them. Alternatively you can sedate her as described in (2) and break the fuses to get the statue afterwards. Go to the elevator and wait for the technician to arrive. When he does, go into the elevator and leave the penthouse.
It is possible to sedate the technician as well if needed, but he sees rather well in darkness and apparently has telepathic abilities to alarm the guards instantly when startled so this is difficult and not recommended.
If you want to have some fun, start with the Ballers SD. Walk straight in and shoot the pianist. Both male and female guards should have noticed you by now. As they rush towards you, shoot them in the head and see them fly. The secretary should be crouching near the table with the NVG on it. If you shoot her in the head from the correct position, she will go flying, crashing through the window and going all the way down (it works, I did it many times). Now kill Charlie in any way you want to (can you shoot him through the glass as well? I never tried). Then destroy the fuses, pick up the items and exit by the elevator. (You may kill the technician too. I never got the backup guards, are they easy to kill?) Of course, don't expect SA by this method.