Ova kuća je veća nego moj stan.

Because they agree with kuća, which is a feminine singular noun.

In Serbian, adjectives and demonstratives usually match the noun in:

• gender
• number
• case

So:

• ova kuća = this house
• veća = bigger/larger in the feminine singular form

If the noun were masculine, you would get:

• ovaj stan je veći = this apartment is bigger

If it were neuter:

• ovo selo je veće = this village is bigger

Yes. Veća is the comparative form of the adjective velik / velika / veliko = big.

The comparative is:

• masculine: veći
• feminine: veća
• neuter: veće

So:

• velika kuća = a big house
• veća kuća = a bigger house

This comparative is somewhat irregular from an English learner’s point of view, because the base adjective is velik, but the comparative becomes veći, not something fully predictable like velikiji.

Nego means than in a comparison.

So:

• veća nego moj stan = bigger than my apartment

It introduces the second part of the comparison, just like than in English.

Yes. A very common alternative is:

• Ova kuća je veća od mog stana.

This also means This house is bigger than my apartment.

The difference is mainly grammatical:

• with nego, Serbian often keeps the compared noun phrase in a nominative-like form:
  • nego moj stan
• with od, the following noun goes into the genitive:
  • od mog stana

So both are natural, but the forms after them are different.

Because after nego, the compared phrase is commonly left in the nominative:

• nego moj stan

If you use od, then you need the genitive:

• od mog stana

Compare:

• Ova kuća je veća nego moj stan.
• Ova kuća je veća od mog stana.

Both are correct; they just use different comparison structures.

Because stan is a masculine singular noun.

The possessive adjective moj changes to match the noun it describes:

• moj stan = my apartment (masculine)
• moja kuća = my house (feminine)
• moje selo = my village (neuter)

So in this sentence:

• moj matches stan
• ova and veća match kuća

Je is the 3rd person singular form of the verb biti = to be.

So the sentence structure is:

• Ova kuća = subject
• je = is
• veća nego moj stan = predicate/comparison

In standard Serbian, you normally need je here, just as you need is in English:

• Ova kuća je veća... = This house is bigger...

Yes, Serbian word order is more flexible than English, but not every order sounds equally natural.

The most neutral order is:

• Ova kuća je veća nego moj stan.

You may also hear variations for emphasis, such as:

• Veća je ova kuća nego moj stan.

But for a learner, the original word order is the safest and most standard.

Usually yes in this kind of sentence. Stan means apartment or flat.

It refers to a dwelling unit, while kuća means house.

So the sentence is contrasting:

• a house (kuća)
• with an apartment/flat (stan)

The adjective and demonstrative would change to match the new noun.

For example, with stan (masculine):

• Ovaj stan je veći nego moja kuća.
• This apartment is bigger than my house.

Notice the agreement:

• ovaj
  • masculine noun
• veći
  • masculine noun
• moja kuća because kuća is feminine

So Serbian keeps agreement very consistently.

A rough guide:

• kuća ≈ KOO-cha, but the ć is softer than English ch
• veća ≈ VEH-cha, again with that soft ć
• nego ≈ NEH-go
• stan ≈ stahn

Two useful letters here:

• ć = a soft sound somewhat between t and ch
• ž (not in this sentence, but common in Serbian) sounds like the s in measure

A native speaker’s pronunciation is softer and more precise than these English approximations, but they are a good starting point.