Ružičasta haljina joj jako lijepo stoji.

That is one of the most common questions.

In Croatian, stajati literally does mean to stand, but it also has an extended meaning when talking about clothes, colors, hairstyles, and similar things:

• Haljina joj lijepo stoji. = the dress looks good on her / suits her
• Plava boja ti dobro stoji. = blue suits you

So in this sentence, stoji does not mean that the dress is physically standing. It means the dress suits her appearance.

Joj is the dative form of ona (she / her), and here it means to her.

Croatian often uses the person affected by the verb in the dative with this kind of expression:

• Haljina joj stoji. = the dress suits her
• literally: the dress stands nicely to her

So joj is not the subject. It tells you who the dress looks good on.

A few related forms:

• mi = to me
• ti = to you
• mu = to him
• joj = to her
• nam = to us
• vam = to you (plural/formal)
• im = to them

In this structure, haljina is actually the subject of the sentence.

Croatian uses this pattern:

• [thing] + [person in dative] + stoji

So:

• Ružičasta haljina = the pink dress → subject, nominative
• joj = to her → dative
• jako lijepo stoji = suits her very nicely

This is different from English, where learners may expect something like The pink dress suits her, with her as the object. Croatian organizes it differently.

Because the adjective has to agree with the noun.

Haljina is:

• feminine
• singular
• nominative

So the adjective must also be:

• feminine
• singular
• nominative

That gives:

• ružičast → masculine
• ružičasta → feminine
• ružičasto → neuter

So ružičasta haljina is the correct agreement.

They do different jobs:

• lijepo = nicely / beautifully / well
• jako = very

So:

• lijepo stoji = looks nice / suits nicely
• jako lijepo stoji = looks very nice / suits very well

Here lijepo is the main adverb describing stoji, and jako intensifies lijepo.

You could compare:

• Haljina joj stoji lijepo.
• Haljina joj stoji jako lijepo.

The second one is stronger.

Yes, Croatian word order is fairly flexible, but there are rules and strong tendencies.

The most important point here is that joj is a clitic. Clitics usually go in the second position in the sentence or clause.

So after the first phrase Ružičasta haljina, you get:

• Ružičasta haljina joj jako lijepo stoji.

This sounds natural and neutral.

Other word orders are possible for emphasis, for example:

• Jako joj lijepo stoji ružičasta haljina.
• Joj ružičasta haljina jako lijepo stoji.
  This can occur, but learners should be careful, because clitic placement is tricky.

For most learners, the safest neutral pattern is exactly the one in your sentence.

Usually not if you want to say who the dress suits.

• Ružičasta haljina jako lijepo stoji.
  This sounds incomplete in most contexts, because it feels like something is missing: looks good on whom?

If the person is extremely obvious from context, Croatian may omit it in conversation, but normally you include the dative pronoun or noun:

• Ružičasta haljina Mariji jako lijepo stoji.
• Ružičasta haljina joj jako lijepo stoji.

So for learners, it is best to keep joj.

Sometimes, but it would not mean exactly the same thing.

• Haljina joj lijepo stoji = the dress suits her / fits her appearance well
• Haljina izgleda lijepo = the dress looks nice

With stoji, the focus is on how the item looks on that person.

With izgleda, the focus is more general: the dress looks nice, but not necessarily in the sense of suiting her.

So stoji is the more idiomatic choice here.

It is mainly about appearance: that the dress looks good on her.

Depending on context, it can also imply that the fit is good, because something usually looks good on someone if it hangs or fits well. But the core meaning is still it suits her.

If you want to talk more directly about physical fit, Croatian may use other expressions too, such as:

• Haljina joj dobro pristaje.
• Haljina joj dobro odgovara.
• Haljina joj je taman. = the dress is just the right size for her

Still, dobro/lijepo stoji is very common and natural for clothes.

Yes, very easily. This is a very productive pattern in Croatian.

Examples:

• Kaput mi dobro stoji. = The coat suits me.
• Ta košulja ti lijepo stoji. = That shirt looks good on you.
• Crvena haljina joj odlično stoji. = The red dress suits her perfectly.
• Ove naočale mu ne stoje baš dobro. = These glasses do not suit him very well.
• Ta boja im lijepo stoji. = That color suits them.

So once you learn the pattern [thing] + [dative person] + stoji, you can use it a lot.

Stoji is:

• present tense
• 3rd person singular
• from the verb stajati

Here it expresses a current or general state: the pink dress suits her.

Croatian present tense is often used the same way English uses the present simple for general truths or present situations.

You could also form other tenses:

• Ružičasta haljina joj je jako lijepo stajala. = The pink dress suited her very well.
• Ružičasta haljina će joj jako lijepo stajati. = The pink dress will suit her very well.

So the form changes, but the same basic pattern stays in place.