If anyone is wondering what weapons should you equip for this mission. The answer is, none if you follow this walkthrough, but if you insist on doing it your own way, I recommend silenced gus since there are tons of guards all over the place.
So the first thing you're gonna have to do is enter the building, and go up the stairs to the second floor and enter the elevator on the left. Climb up the hatch and wait, your first target will enter the elevator not long after and you can strangle him from above using your fiber wire. Then take his keycard (803) and also the suitcase. Then just go back to the ground floor and go back to the second elevator, the one on the right.
Do the same thing and climb up the hatch. Wait for the second target, Hendrik Schmutz to enter and strangle him just like you did with the other dude. Take his clothes and keycard, and also leave the Payment Briefcase, all your guns and bombs there. You will get them back later.
When you assassinate the second target, you may proceed the the 7th floor, go find this guy's room, 707 and use his keycard to enter. Inside, just in front of the door you'll find a DNA briefcase take it with you. Now you have to go to the 8th floor.
For some people, you may not reach the 8th floor using the elevator so go find the balcony at the 7th floor, you can climb up from there. If there happens to be someone there smoking don't give a shit about him, but to be safe, you can save. Anyway, when you reach the 8th floor activate the fire alarm near room 803 (one of your targets room) all the guards will run to the elevator, use that chance and enter the room using the keycard.
Go inside the room and you will see there's a phone on the table, use the phone to call your third target. Your third target will then leave the casino lounge and go outside. Hurry up and leave the room, use the elevator to get to the lobby, enter the casino. Use the door at the east side to avoid getting caught on camera. Hurry up and reach the other side. Then just go to the lounge, before you enter you'll have to get scanned by the security, if you refuse to get scanned and just dash in, you'll probably die. Let the security scan you and hurry up to the exit at the other side, follow the stairs and you'll either find him still outside or coming back to the lounge, that's when you kill him, you can also leave the DNA Briefcase there.
With all your targets gone, go back to the elevator and take all your guns and SUIT UP! Then you can leave the place.
