Trebalo bi pomesti blagovaonicu prije večere.

Trebalo bi means should or ought to.

In this sentence, it gives a recommendation or mild obligation:

• Trebalo bi pomesti blagovaonicu prije večere.
  = The dining room should be swept before dinner.

This is a very common Croatian way to express what would be advisable or appropriate.

Because this is an impersonal construction.

When Croatian uses trebati in the sense of it is necessary / one should, it often appears in the neuter singular form:

• treba = it is necessary / should
• trebalo bi = it should / one should

So trebalo here does not refer to a masculine person or thing. It is the default neuter form used in impersonal statements.

Compare:

• Trebao bih pomesti blagovaonicu. = I should sweep the dining room.
  Here trebao agrees with I (masculine speaker).
• Trebalo bi pomesti blagovaonicu. = The dining room should be swept / One should sweep the dining room.
  No specific person is named.

Bi is a marker of the conditional mood.

It helps create the meaning of:

• would
• should
• ought to

So:

• treba = need(s) to / it is necessary
• trebalo bi = should / ought to / it would be good to

This makes the sentence softer and less direct than a plain statement of necessity.

Pomesti means to sweep.

More specifically, it is a perfective infinitive, so it suggests a completed action: to sweep something up / to get the sweeping done.

Croatian often has verb pairs like this:

• mesti = to be sweeping / to sweep in a more general or ongoing sense (imperfective)
• pomesti = to sweep up, to sweep completely (perfective)

In this sentence, the perfective verb fits well because the idea is to complete the task before dinner.

Because after trebalo bi, Croatian commonly uses an infinitive to express the action that should be done.

Structure:

• trebalo bi + infinitive

So:

• trebalo bi pomesti = should sweep / should be swept

This is very similar to English should + verb.

Because blagovaonicu is the accusative singular, used here for the direct object of the verb pomesti.

Base form:

• blagovaonica = dining room

In the sentence, the dining room is the thing being swept, so it goes into the accusative:

• pomesti blagovaonicu = to sweep the dining room

This is a feminine noun ending in -a, so:

• nominative singular: blagovaonica
• accusative singular: blagovaonicu

Večere is in the genitive singular.

That is because the preposition prije (before) requires the genitive:

• prije večere = before dinner

So:

• nominative: večera = dinner
• genitive: večere

This is a very common pattern in Croatian:

• prije ručka = before lunch
• prije sastanka = before the meeting
• prije večere = before dinner

Yes, in normal usage it usually just means before dinner in the practical sense: before the evening meal happens or before people sit down to eat.

Like in English, the exact timing depends on context. It does not usually need a more precise explanation unless the situation requires it.

Grammatically, it uses an impersonal construction, but in meaning it often feels close to English passive:

• Trebalo bi pomesti blagovaonicu. = The dining room should be swept. = Someone should sweep the dining room.

Croatian does not need a true passive form here. The impersonal trebalo bi + infinitive is very natural.

Yes. That would also be natural.

The difference is roughly:

• Treba pomesti blagovaonicu prije večere.
  = It is necessary to sweep the dining room before dinner / The dining room needs to be swept before dinner.
• Trebalo bi pomesti blagovaonicu prije večere.
  = The dining room should be swept before dinner / It would be good to sweep it before dinner.

So trebalo bi sounds a bit softer, more like advice or a recommendation.

Yes. Croatian word order is quite flexible.

The neutral order here is:

• Trebalo bi pomesti blagovaonicu prije večere.

But you could also hear:

• Blagovaonicu bi trebalo pomesti prije večere.
• Prije večere trebalo bi pomesti blagovaonicu.

These versions shift the emphasis a little:

• putting blagovaonicu first highlights the dining room
• putting prije večere first highlights the time

The original sentence is a very natural default order.

No. Blagovaonica is a standard word for dining room, but depending on region and variety, learners may also come across other words.

Still, in this sentence, blagovaonica is perfectly normal and clear.

No, it is neutral and natural.

It is not slang, but it is also not overly formal. You could use it in everyday speech or writing when making a practical suggestion or stating what ought to be done.

Because Croatian often leaves the agent unspecified when it is unimportant, obvious, or general.

So the sentence focuses on what should be done, not who should do it:

• Trebalo bi pomesti blagovaonicu prije večere.
  = The dining room should be swept before dinner.

If you wanted to specify the person, you would use a different structure, for example:

• Trebali bismo pomesti blagovaonicu prije večere.
  = We should sweep the dining room before dinner.