Na zidu u dnevnom boravku stoji stara slika.

Because na can take different cases depending on meaning:

• na + accusative = movement onto something
  
  • Stavljam sliku na zid. = I am putting the picture onto the wall.
• na + locative = location on something
  
  • Slika je na zidu. = The picture is on the wall.

In your sentence, the picture is already located there, so Croatian uses the locative: na zidu.

For the same basic reason: u changes case depending on whether you mean movement or location.

• u + accusative = motion into
  
  • Ulazim u dnevni boravak. = I am going into the living room.
• u + locative = location in
  
  • U dnevnom boravku... = in the living room

Since this sentence describes where something is, u takes the locative: u dnevnom boravku.

Because adjectives in Croatian must agree with the noun they describe in:

• gender
• number
• case

Here, boravak is masculine singular, and after u in a location meaning it becomes locative singular: boravku.

The adjective dnevni must match it, so it also changes to locative singular masculine: dnevnom.

So:

• dnevni boravak = nominative
• u dnevnom boravku = locative

This is a very common thing for English speakers to notice.

In Croatian, stajati / stoji often means not only to stand upright, but also more generally to be positioned, to be located, or to sit there somewhere.

So stoji stara slika can mean something like:

• an old picture stands there
• an old picture is there
• an old picture is positioned there

It sounds more natural in Croatian than a literal English translation might suggest.

That said, for a picture on a wall, many speakers might also say visi (hangs):

• Na zidu u dnevnom boravku visi stara slika.

That is often even more specific and natural for something hanging on a wall.

Yes. You could say:

• Na zidu u dnevnom boravku je stara slika.

That simply states that the picture is there.

Using stoji gives a slightly stronger sense of physical presence or position. It is often more vivid than just je.

So:

• je = neutral existence/location
• stoji = located there, standing/positioned there
• visi = hanging there

Because it is the subject of the sentence.

The thing that stoji is stara slika, so it stays in the nominative singular:

• stara = feminine singular nominative
• slika = feminine singular nominative

The prepositional phrases na zidu and u dnevnom boravku just tell you where the subject is.

That version is also correct.

Croatian word order is much more flexible than English word order. The sentence you were given:

• Na zidu u dnevnom boravku stoji stara slika.

puts the location first, then the verb, and introduces the subject at the end. This is a very natural way to present information in Croatian.

It can feel like:

• On the wall in the living room, there is an old picture.

So the chosen word order helps organize information:

• known setting first: Na zidu u dnevnom boravku
• new or important item later: stara slika

They are very close, and in many contexts both mean in the living room.

But there can be a slight nuance:

• dnevni boravak = living room / lounge / sitting room
• dnevna soba = living room, often a more everyday term

In many situations, they are interchangeable. A learner will hear both.

So you could also say:

• Na zidu u dnevnoj sobi stoji stara slika.

and it would be perfectly normal.

Slika is a broad word. It can mean:

• picture
• painting
• image

Depending on context, it could refer to artwork on a wall, not necessarily a photograph.

If you specifically want photograph, Croatian often uses:

• fotografija
• sometimes slika in everyday speech as well

So in this sentence, stara slika most naturally suggests an old picture/painting on the wall.

Because Croatian has no articles.

So stara slika can mean:

• an old picture
• the old picture

The exact meaning depends on context.

English requires an article, but Croatian usually lets the situation make that clear.

It is the locative singular of zid (wall).

The basic form is:

• zid = nominative singular

After na with a location meaning, it becomes:

• na zidu = on the wall

So yes, zidu is just the locative form of zid.

It gives two nested location phrases:

• na zidu = on the wall
• u dnevnom boravku = in the living room

Together they mean that the picture is on a wall, and that wall is in the living room.

So the structure is basically:

• on the wall
• in the living room
• stands an old picture

This layering of place expressions is very normal in Croatian.

Grammatically, yes, but it sounds less clear.

Placing u dnevnom boravku right after slika can make it briefly sound as if the picture itself is somehow in the living room rather than specifically the wall being in the living room. The original order is smoother and more natural:

• Na zidu u dnevnom boravku stoji stara slika.

Croatian often puts related location phrases together before the verb.

The dictionary form is stajati.

Here are the relevant forms:

• stajati = to stand / to be situated
• stojim = I stand
• stojiš = you stand
• stoji = he/she/it stands

In your sentence, slika is singular, so the verb is also singular: stoji.

Yes.

The adjective star changes to match the noun:

• star zid = old wall (masculine)
• stara slika = old picture (feminine)
• staro ogledalo = old mirror (neuter)

Since slika is feminine singular, the adjective becomes stara.

So stara slika is a good example of adjective-noun agreement in Croatian.