Ako ti se sutra bude išlo u šetnju, možemo prošetati do rijeke i usput kupiti pecivo.

This uses a very common Croatian pattern:

• nekome se ide / ne ide = someone feels like going / doesn’t feel like going
• literally, something like to someone, it goes

So:

• ti = to you (dative)
• se = part of this impersonal expression
• bude išlo = will feel like going
• u šetnju = for a walk

So the whole first part means If you feel like going for a walk tomorrow.

Because after ako when talking about a future condition, standard Croatian usually uses future II, not ordinary future I.

So Croatian says:

• Ako ti se sutra bude išlo... = If you feel like going tomorrow...

not normally:

• Ako će ti se...

The form bude išlo is the future-II structure here. English does something similar in a different way: we usually say If you feel like going tomorrow, not If you will feel like going tomorrow.

Because this is an impersonal construction.

There is no normal nominative subject like ja, ti, on, etc. In these impersonal expressions, Croatian often uses the neuter singular by default:

• Spavalo mi se. = I felt sleepy / I felt like sleeping.
• Radilo mu se. = He felt like working.
• Išlo ti se. = You felt like going.

So išlo is neuter singular because the sentence is built impersonally, not because it refers to some neuter noun.

Here se is not really reflexive in the English sense of oneself.

It is part of the fixed impersonal pattern:

• ide mi se
• ne ide joj se
• bude nam se išlo

This pattern expresses an internal urge, wish, or inclination. So se helps build the meaning feel like doing something.

You should learn ti se bude išlo as a chunk.

Because the person who experiences the feeling is expressed in the dative in this construction.

Compare:

• mi se ide = I feel like going
• ti se ide = you feel like going
• mu se ide = he feels like going
• nam se ide = we feel like going

So ti does not mean you as a subject here. It means to you, roughly: If it feels like going to you tomorrow...

That sounds odd in English, but it is normal in Croatian.

Because u šetnju shows motion toward something, so it takes the accusative.

• u šetnju = into / for a walk
• u šetnji = in a walk / while on a walk

Here the idea is go for a walk, so Croatian uses:

• ići u šetnju

This is just the normal idiom. English says go for a walk, but Croatian says go into a walk, so to speak.

Normally the usual expression is ići u šetnju.

A learner should definitely remember:

• ići u šetnju = to go for a walk

Using na šetnju would sound unusual in this context.

This is mainly about aspect.

• šetati = imperfective
  meaning ongoing/repeated walking, walking around, being in the process of walking
• prošetati = perfective
  meaning to take a walk, go for a walk as one complete event

In this sentence:

• možemo prošetati do rijeke

means we can take a walk to the river.

It sounds like one complete outing. If you used šetati, it would sound more like the activity in progress or a general habit.

Because the speaker is suggesting one specific completed action: a walk to the river.

• možemo prošetati do rijeke = we can take a walk to the river
• možemo šetati do rijeke would sound less natural here, because šetati focuses more on the ongoing activity, not the whole outing as a single event

So prošetati fits the idea of a planned little trip better.

In Croatian, the present tense of a modal verb like moći can refer to the future when the time is already clear from context.

Here sutra already tells you this is future time, so:

• možemo prošetati = we can / we could / we’ll be able to take a walk

It is a natural suggestion, not a literal present-time statement.

It is closer to a friendly suggestion like we can or we could.

So:

• Ako ti se sutra bude išlo u šetnju, možemo prošetati do rijeke...

sounds like:

• If you feel like going for a walk tomorrow, we can/could walk to the river...

If the speaker wanted to sound a bit softer or more tentative, they might say:

• mogli bismo prošetati... = we could take a walk...

After do, Croatian uses the genitive.

So:

• rijeka = river
• do rijeke = to the river / as far as the river

That is why the form is rijeke, not rijeka.

Usput means on the way, along the way, or while we’re at it.

So:

• i usput kupiti pecivo = and buy some pastry/bread on the way

It is an adverb, and it often appears in this kind of sentence to add a convenient extra action.

Yes, word order is fairly flexible.

For example:

• i usput kupiti pecivo
• i kupiti pecivo usput

Both are possible. The version in your sentence is very natural and neutral.

Pecivo is a general word for a baked item such as:

• a roll
• a pastry
• some bakery item

The exact translation depends on context. In this sentence, buying something from the bakery on the way is the basic idea.

Not necessarily.

Croatian often leaves this a bit general. Kupiti pecivo can mean:

• buy a pastry
• buy some pastry
• buy a bakery item

There are no articles in Croatian, so the exact English version depends on context. If the speaker wanted to be clearly plural, they could say:

• kupiti peciva = buy some pastries

Because both ti and se are clitics: short unstressed words that usually go near the beginning of the clause in a fixed order.

In standard Croatian, this order is natural:

• Ako ti se sutra bude išlo...

The dative clitic (ti) normally comes before se.

So ti se is the expected order here.

Because Croatian clitics tend to appear very early in the clause, often immediately after a clause-opening word like ako.

So:

• Ako ti se sutra bude išlo...

is the natural placement.

This early-clitic position is one of the things English speakers often need time to get used to.

Because both depend on možemo.

The structure is:

• možemo prošetati do rijeke
• i (možemo) usput kupiti pecivo

Croatian often leaves the second možemo unstated because it is already understood.

So the full idea is:

• we can take a walk to the river and buy some pastry on the way

You may hear forms like that in speech, but for a future condition after ako, standard Croatian prefers:

• Ako ti se sutra bude išlo u šetnju...

So if you are learning standard, careful Croatian, bude išlo is the best choice here.

Not exactly.

• otići do rijeke = go to the river
• prošetati do rijeke = walk to the river as a pleasant walk

So prošetati adds the idea that the walk itself is part of the plan, not just reaching the river.

Because the sentence begins with a subordinate if-clause:

• Ako ti se sutra bude išlo u šetnju, ...

After that clause, Croatian normally uses a comma before the main clause:

• možemo prošetati do rijeke i usput kupiti pecivo

So the comma works much like in English: If..., then...