Here's the walkthrough explained step by step; For further details watch the video!

1) Give the badge to Danielle Pierson
2) Take the elevator up
3) After the storytelling talk to Charlotte Ragagli and collect the USB Drive
4) Take the elevator down
5) Pick up the pencil above Paul Romano's desk
6) Examine the USB Drive to have a hint to obtain the password
7) Insert the USB Pen Drive into Paul Romano's PC
8) Enter the password "MONKEY"
9) Take the dossier from the printer
10) Examine the dossier to unlock the Bob Soap's residence
11) Talk to Marion Simmons about the pencil sharpener and accept to help her
12) Combine the noteblock with the pencil
13) Give the noteblock with the phone number to Marion Simmons
14) Pick up the pencil sharpener
15) Reach your apartment
16) Take the blank sheet above the desk
17) Take the pills for headache in the kitchen
18) Collect the garage's key
19) Combine the pencil with the blank sheet
20) Combine the resulting sheet with pencil with the pencil sharpener to obtain the graphite powder
21) Use the graphite powder to lubricate and unlock the garage's door
22) Use the garage's key to enter into the garage
23) Collect the holed iron slabs inside the garage
24) Reach the Charlie's Pub
25) Take the mug above the barrel
26) Collect the pool cue from the game room
27) Go to the Bob Soap's residence
28) Pick up the noose from the wall
29) Combine the rope with the holed iron slabs
30) Combine the resulting slabs and rope with the pool cue
31) Use the reinforced pool cue to remove the wooden planks from the entrance and proceed inside the apartment
32) Collect the syringe
33) Pick up the bible
34) Examine the bible and take the club's card
35) Return to the Charlie's pub
36) Ask to Charlie Romano about the Reverend Robert
37) Show to Sylvie Bond the club's card
38) End the chess game by moving E7 to G6
39) Go to the church
40) Collect the lighter from the side nave
41) Reach the club 'THE HELL' and examine the poster near to Marcel Andrews
42) Insert the club's card inside the crack
43) Answer this way to the knocking: 1 4 3 2 2 3 (*)
44) Collect the empty bottle inside the club
45) Pick up the funnel near the henchman
46) Talk to Bob Soap and reach an agreement with him (1st choise and then 4th choise)
47) Talk to Serena Monterrey about the HELLISH drug
48) Return to your apartment
49) Use the mug with the skin in the kitchen
50) Combine the pills for headache with the mug full of water
51) Combine the empty bottle with the funnel
52) Pour the contents of the mug inside the bottle
53) Come back to the TiBRAIN's offices
54) Talk to Jacob Redfield about his lava-lamp
55) Take the lava-lamp
56) Come back to the Charlie's pub
57) Talk to Charlie Romano about the ingredient for the drug
58) Use your wallet with Charlie Romano to obtain the whiskey
59) Pour the contents of the whiskey bottle inside the bottle with funnel
60) Pour the contents of the lava-lamp inside the bottle with funnel
61) Use the lighter to sterilize the syringe
62) Combine the sterilized syringe with the bottle containing the HELLISH drug
63) Return to the club THE HELL
64) Give the dose of HELLISH to Bob Soap
65) After the storytelling defeat Bob Soap
66) Enjoy the ending!

(*) 43. the first line of the poster contains the "request" (11 12 11 or 1 1 1 2 1 1) that is the equivalent of the numers of knocking you hear (4 knock - 2 knock - 2 knock - 2 knock - 3 knock - 3 knock or 4 2 2 2 3 3);
the second line of the poster contains the "suggestion/solution" of the puzzle (31 12 21 or 3 1 1 2 2 1), that is the equivalent of the answer to give (1 4 3 2 2 3);
The concept behind this puzzle is that you have to undertand that the two lines of the poster are in reality a numerical sequence (and not a date and a time);
So, if the first line (question) is 1 1 1 2 1 1 and second line (solution) is 3 1 1 2 2 1, is because the first line is composed by 3 times the number 1, 1 time the number 2 and 2 times the number 1 (3-1 1-2 2-1)
If we would like to continue this numerical series, the third line after 3 1 1 2 2 1 will be 1 3 2 1 2 2 1 1 and so on;
In conclusion, if you hear 4 2 2 2 3 3 knocking (question), the solution is 1 4 3 2 2 3.