Solution:

It's a Murder.

Explanation:
1. There is a sign of the struggle in the room.

2. In case of suicide, bullet wound is generally on the head but here the wound is on the chest.

3. The dead man is left handed as all his the stuff like phone pens are on the left side but the gun is on the right-hand side (must be planted).

Solution:

This riddle is perspective riddle where reader perspective determines if it's a murder or suicide.

A) Evidence suggests its a Murder
1. There are many signs that suggest struggle in the room.

2. The dead man seems to be left handed as all the essential things like the glass of water, the laptop is placed on the left-hand side and the murderer not knowingly that man was a left-handed placed gun on the right side.

3. We can see a man running in the background and probably run after opening the window.

B) Evidence suggests its a Suicide
The guy was frustrated and bankrupt(In the picture we can see some sort of financial data which going down like anything). He got drunk. and smacked the bottle into the wall with frustration and threw everything on the floor.
He then writes a suicide note and placed it on the table.
Pulls out a gun and shoot himself.
Note: Also about the man running, fingerprint and man running direction does not match

My perspective answer: Its a murder.

Solution:

Number 3

Explanation:
Since it's a ladies bathroom, so only ladies can enter the bathroom and hence most likely the killer.

Solution:

Costa

Explanation:
Costa brings the dagger made of ice in the thermos so it won't melt. He killed the Michy with the dagger and then the dagger melts with time.

Solution:

Bond was suspicious of the women as one never knocks its own door at the hotel.

Solution:

Costa

Explanation:
c + 1 characters-> d
o + 2 characters-> q
s + 3 characters-> v
t + 4 characters-> x
a + 5 characters-> f

=> dqvxf = costa

Solution:

Ruppell's vulture generally found on high altitude and Mr. smith was on the plane. The vulture hit the plane and the plane got crashed.

Solution:

Dean Winchester shoots himself in the mirror.

Solution:

The dead guy is Superman. He died because he was exposed to a Kryptonian rock.

Solution:

Since the knife was in her hand which implies that she was planning to kill her husband "Inspector Montalbano".