's

[Daniellll]

when I am talking about a thing and not a person should I use the " 's " ?
for example :
do we say: "the world cup final" or the "world cup's final" ?
do we say: "where is the link to your apartment pictures?" or "where is the link to your apartment 's pictures?" ?

[Heterological]

It is proper to use nouns as adjectives when other nouns "belong" to them. The final is of the World Cup; therefore, we write, "the World Cup Final." The pictures are of your apartment, so we write, "your apartment pictures" (although it would be a little more natural to just say, "pictures of your apartment.") We only use 's when real ownership applies--when an object is possessed by someone or something. Finals don't belong to the World Cup; pictures aren't owned by the apartment.

Examples of real ownership:
"My aunt's ring" (the ring belongs to my aunt)
"The company's headquarters" (the headquarters* belongs to the company)
"The store's merchandise" (the merchandise belongs to the store)

In the above examples involving things, it would also be correct to write, "company headquarters" and "store merchandise." I'll see if I can think of a case in which a thing possessing a thing can't be written as "thing thing" as well as "thing's thing." In any case, do not use 's for the examples you gave.

*"headquarters" looks like it's plural, but it's actually singular

[Tdol]

Headquarters is sometimes used as a plural in BrE.