Is there a way to create a map with objectives in the editor? Something with an end. Everything that I created are endless.

learn how to script:

http://www.stranded.unrealsoftware.de/s2_mods.php

yeah you have to write the end.

good luck.

From the 332 commands, which one is the best to be used?

how the hell do you define "better"?

it depends on what you want to do but unless you dont make a clear statement about that there is no way to tell which of maybe several possible implementations would be the best/most effective.

I want to know how to create an objective in the map and the command necessary.
Just for example like the one used in Raptor Hunter or having collected a certain amount of something in order to end a game.