As dev said:

You can use your inventory items with "hand" icon. Also, you can grab or use items with hand icon. You can inspect items, locations with magnifying glass icon. You can talk to characters with lips icon. You can access these icons by right click or spinning mouse wheel.

You can also "walk fast" if you double click (left mouse button) on position on the screen.
Clicking ? icon, second from right, at top of screen, will display current objective - it's partially a hint.

To make game in window or bigger screen, go to game's directory. You can do that by clicking right mouse button on the game in Steam's Library, then "Properties", then change tab to "Local Files" and then click on "View local files...". There should be winsetup.exe - launch it by double clicking its icon. Note: If you "Save and Run", you won't have Steam overlay.
If you want game screen to be stretched to your resolution use similar options like this:

Click = no special icon
Use/Pick = hand icon
Examine/Search = magnifying glass icon
Talk = speech bubble icon
Use <itemname> = Click item's icon on...
Left part = the thing you need to look is on left part of your screen, or you need to move your cursor there.
Leave area = usually it will mean to go to map.
I don't point out when are cutscenes (to avoid spoilers), but usually where gaps in text are... somethings happening.

Actions might be optional (I'm not sure if it's meaningful for progression of the game). If you have more info, please share.

01) Click arrow that appears after pointing bottom part of screen to leave area - choose Guest House on the map.
02) Use door.
03) Leave house (bottom part). Leave area (left part). Enter shore.
04) Try examining these things: boat, dock, left rocks, right rocks.
05) Leave area (usually it's connected with using map) .

DAY 1
06) Leave house. Go to shore.
07) Click sea - it's active-point is slightly to the left of dock, but below boat.
08) Tell Bora (he's that dude) to pick up the phone.
09) Leave area. Go to forest (it's "earthquake's site" on the map). Wait...
10) Examine giant crack. (No, it's not about her cleavage).
11) Tell Bora to pack the gear.
12) Leave area (down-right part).
13) Go to guest house. Enter it.
14) Go upstairs. Go to your room - it's middle door on right side.
15) Use laptop. Use EQ icon. Click red dot, then point location as seen on the map before (from center of the map, a bit on right and top).
16) Leave room, go downstairs. Enter kitchen. Use oven.
17) Leave kitchen. Examine guest book (on the counter, right side).

DAY 2
18) Leave room, go downstairs.
19) Take key, go upstairs. Use key on right door.
20) Examine writing desk. Leave room. Go downstairs.
21) Leave house. Leave area. Go to forest (earthquake's site). Go to giant crack area (top right part of screen).
22) Tell Bora to prepare equipment.
23) Use hammer on piton (it's that wood in the ground, holding the rope).
24) Use piton on giant crack.
25) Use piton on ground.

26) Use laptop. Click pigeon logo. Click "Fatma".
27) Click "Add" and enter Mehmet's number: 4421587. Click "Mehmet".
28) Quit laptop. Pick up smartphone (above laptop, near window). Use phone on the egg.
29) Use laptop. Click bluetooth icon (last icon). Click phone.
30) Go to Pigeon, then attach file by clicking folder icon, then choosing "vid01.mp4".
31) Leave room.
32) Talk to everyone.

DAY 3
33) Leave room. Go downstairs. Leave house.
34) Go to next area (top right). Leave this area (left).
35) Use phone on red seismograph.
36) Proceed to second giant crack (next area).
37) Leave area (left part of screen). Go to Recep's house.
38) Talk to Recep (about everything). Leave area. Go to "Ancient Tomb". Use notebook on tombstone.
39) Leave area, go to guest house, enter it, go upstairs, to your room (middle door).
40) Use laptop. Use EQ icon. Click red dot, then point location as seen on the map before (it's a little to the left and bottom from center of the map).
41) Click red dot, then point on the shore (left bottom part of map).

DAY 4
42) Leave kitchen, then house, then area and travel to shore. Wait.
43) Travel to guest house. Wait... enter house.
44) Go upstairs, enter Bora's room (top door) and talk with him. Leave house.
45) Travel to Recep's house, then try to take logs (the ones closer to Recep).
46) Travel back to guest house. Go upstairs to Bora. Use log on him.
47) Talk with Bora about fingerprints. Go downstairs.
48) Talk with Ebru. Use key on her room - upstairs, door on left side.
49) Open (use) wardrobe. Use hanger on wardrobe. (You might need to examine wardrobe first).
50) Leave Ebru's room and enter to Bora's room. Give him powder.
51) Leave Bora's room and enter your room. Take photos of fingerprints (use your phone on them).
52) Use laptop, then bluetooth icon to import photos. Then use "Photo Match" icon.
53) Solve puzzle, by adding unknown person's fingerprint to one side and suspected person to other side of window.
54) It's Recep. Exit laptop screen.

55) DAY 5. Go downstairs. Go outside and travel to Recep's house.
56) (unsure what to do here) Wait or examine bush to right side. There should be arrow next to tree (left side of it), allowing to proceed to next area.
57) Use tape in inventory. Then use tape scrap on baby powder. Use tape in inventory, again.
58) Use Recep's fingerprint on both consoles. Do it again - on the door inside the room.
59) Go left (there's no arrow - so just click near left edge of screen). Use fingerprint on console. Enter room.
60) Click bottom part of screen. Search (use) surgical instruments. Leave area (I hope you know how, at this stage of game...).
61) Go to area where Bora's trapped. Use scalpel on door.
62) Talk with scientist (about everything). Click bottom part of screen to exit.
63) Use ladder. Use tape with powder on scientist. Use ladder to go up.
64) Click right side. Click the alley to the left (with "Y" on building). Use fingerprint of scientist on console. Enter room.
65) Use keyboard (it's between consoles, in front of chair).
66) Escape door puzzle. Set middle voltage to the number above. Use buttons on the side.
Solution below
Top line: 1.3 / 1.9
Middle line: 7.0 / 4.0
Bottom line: 12 / 16
67) Exit the room.