Water heater problem
Did you ask the maintenance guy what he did to "fix" it the first two times?

This should give a pretty good clue as to what might have gone wrong.

Seeing the picture we can see that this is a natural gas water heater. Is it possible that the pilot is going out?

Pilot lights can be going out for a number of reasons:

1) The water tank is old and holes have rusted into the bottom and water is dripping out and extinguishing the pilot light flame.

2) The thermo sensor has gone bad and requires replacement. This is usually thin tube that runs from the gas control valve over to the pilot flame. The flame keeps the sensor end hot and keeps the gas valve armed. If the flame goes out this forces the gas valve off as a safety interlock.

3) A draft by the floor is causing the pilot light flame to go out. The missing cover  over the pilot light access hole could be the cause of this problem.

As a very first check of your missing hot water kneel down and look into the access hole and see if the pilot light is going.

Since you live in an apartment I assume that you rent. If this is the case you should certainly not be trying to fix this problem yourself. That would be the responsibility of the landlord. If you are in an owner occupied apartment then that is another issue and your best course of action would be to call in a technician to perform the proper repairs or replacement of the water heater.