Trying to switch 2 prong socket to 3 prong socket
Guatemala uses the same power standards as the USA.  Anyone can do anything, but I'd expect to see US style wiring colors, and not old UK style.  In the US:


Ground = green or bare  (green screw)
Neutral = white or gray (silver screw) 
Hot = any other color (brass screw) 


Ever buy a new smart phone and the buttons and headphone jack are in totally different positions? Electrical outlets are like that too, every manufacturer puts the screws in different positions.  A common newbie mistake is plugging wires into the new socket based on their position on the old.  Nope, you're looking at the wrong thing. Look at the color of the screw terminals.

Now you know how to identify and move wires from an old outlet to a new one. 

If you are using the backstab/wire-jab connections, don't, even if the last guy did.  If they are backstabs that must be tightened by turning the nearest screw, those are OK.

Looking at wires coming up to the outlet matters too.  Look at what else is happening inside the box itself.  Also look at how the wires coming into the box are grouped.  

Only one green/ground is normal, as all the grounds areenormally spliced together inside the box, with a lone pigtail coming out to the outlet.   Two whites but only one black is unusual.  Find out what's going on there.  It could be that someone is abusing a bare wire as a neutral.  

If you want us to help get to the bottom of it, tell us the map of how the wires enter the box, and in what groups, and any splices occurring inside the box.