Moj susjed je jutros popravio kosilicu i rekao da će sutra pokositi svu travu.

Moj susjed is in the nominative singular, because it is the subject of the sentence: my neighbor.

• moj = my
• susjed = neighbor

Both words are masculine singular nominative here.

You would only use a different form such as susjeda in another grammatical role, for example as an object:

• Vidim svog susjeda = I see my neighbor

So in this sentence, Moj susjed is simply the standard subject form.

Je is the auxiliary verb to be, used to form the perfect tense in Croatian.

So:

• je popravio = has repaired / repaired
• je rekao = has said / said

In natural English, both are usually translated as simple past:

• My neighbor repaired... and said...

Croatian often uses the perfect where English uses the simple past.

In coordinated verbs, Croatian often uses the auxiliary only once if it applies to both verbs.

So:

• Moj susjed je jutros popravio kosilicu i rekao...

means:

• My neighbor repaired the lawnmower this morning and said...

The second je is understood and does not need to be repeated. You could think of it as:

• je popravio i (je) rekao

This is very common and natural.

Popravio is the masculine singular past active participle of popraviti.

It agrees with the subject:

• susjed is masculine singular
• therefore the verb form is popravio

Compare:

• Moj susjed je popravio = masculine singular
• Moja susjeda je popravila = feminine singular
• Moji susjedi su popravili = masculine plural / mixed plural

So the ending -o here helps show that the subject is masculine singular.

Because kosilicu is the accusative singular form, and the lawnmower is the direct object of popravio.

• nominative: kosilica
• accusative: kosilicu

Croatian changes noun endings depending on grammatical role. Since the lawnmower is the thing being repaired, it must be in the accusative.

Jutros means this morning.

It is an adverb of time, telling us when the action happened:

• je jutros popravio = repaired this morning

It does not change form here. It is simply an adverb, not a noun in a case form.

This is a reported-speech structure:

• rekao = said
• da = that
• će pokositi = will mow

So:

• rekao da će sutra pokositi... = said that he would/will mow tomorrow...

Croatian commonly uses da to introduce a clause after verbs like say, think, know, hear, and so on.

Both are possible in Croatian, but će pokositi is the normal form when the infinitive is present in full.

Future I is made with:

• a present-tense form of htjeti as an auxiliary
• plus the infinitive

So:

• će pokositi = will mow

You may also see forms like:

• pokosit će

That version is also correct, but with many verbs the more neutral and common order in a clause like this is će + infinitive.

Also, after da, će pokositi sounds especially natural:

• rekao da će pokositi

This is about aspect, which is very important in Croatian.

• kositi = imperfective, focusing on the process, repeated action, or ongoing activity
• pokositi = perfective, focusing on completing the action

In this sentence, the idea is that tomorrow he intends to finish mowing all the grass, so the perfective verb pokositi is the natural choice.

Similarly:

• popraviti is perfective, meaning to repair/fix successfully, to completion
• popravljao or popravljati would focus more on the process

Croatian often leaves out subject pronouns when the subject is already clear from context.

Here, after Moj susjed ... rekao da će..., it is naturally understood that he is the one who will mow the grass.

So:

• rekao da će sutra pokositi... = said that he would mow tomorrow...

You could add on for emphasis or contrast:

• rekao da će on sutra pokositi svu travu
  This might suggest emphasis, such as he himself will mow it.

But in a neutral sentence, leaving on out is more natural.

Svu travu means all the grass.

Both words are in the accusative singular feminine because they go together, and the whole phrase is the direct object of pokositi.

• nominative: sva trava
• accusative: svu travu

Here:

• svu is the accusative singular feminine form of sav = all / whole
• travu is the accusative singular of trava

So the agreement is:

• svu
  • travu

Because trava is feminine singular, and the adjective/pronoun must agree with it.

Forms of sav vary:

• masculine singular accusative (animate): svog / svega depending on structure
• neuter singular: sve
• feminine singular: svu
• plural forms differ as well

Since travu is feminine singular accusative, the correct matching form is svu.

So:

• svu travu = correct
• sve travu = incorrect

Travu is accusative singular of trava.

It is in the accusative because it is the direct object of pokositi:

• he will mow what?
• svu travu

That is why you see:

• nominative: trava
• accusative: travu

No, Croatian word order is fairly flexible, although some orders sound more natural than others.

The original sentence:

• Moj susjed je jutros popravio kosilicu i rekao da će sutra pokositi svu travu.

is very natural.

But other variations are possible, for example:

• Moj susjed je popravio kosilicu jutros i rekao da će sutra pokositi svu travu.
• Moj susjed je jutros popravio kosilicu i rekao da će pokositi svu travu sutra.

These may shift emphasis slightly. In normal usage, time words like jutros and sutra are often placed where they sound most natural or where the speaker wants to highlight them.

This is mainly an English issue, not a Croatian one.

Croatian says:

• rekao da će sutra pokositi...

Literally, that is:

• said that he will mow tomorrow

But English often shifts the tense after a past reporting verb:

• He said that he would mow tomorrow

Croatian usually keeps će + infinitive in this kind of sentence. So the Croatian structure does not have to mirror English tense backshifting exactly.

Normally, no. After rekao in this type of sentence, da is the standard way to introduce the content clause.

So:

• rekao da će sutra pokositi svu travu = correct

Without da, the sentence would sound wrong or incomplete in standard Croatian.

Yes, they are different kinds of verb forms.

• popravio = past participle used with je to form the perfect tense
• pokositi = infinitive, used with će to form the future

So:

• je popravio = repaired / has repaired
• će pokositi = will mow

This is a very common contrast in Croatian:

• past: auxiliary biti
  • past participle
• future: auxiliary htjeti
  • infinitive

Broadly yes: both are adverbs of time.

• jutros = this morning
• sutra = tomorrow

They tell us when something happens:

• je jutros popravio = repaired this morning
• će sutra pokositi = will mow tomorrow

But they refer to different time frames:

• jutros points to a part of today
• sutra points to the next day

Yes, it is completely natural.

It uses very common and standard patterns:

• possessive + noun: Moj susjed
• perfect tense: je popravio
• direct object in accusative: kosilicu
• coordination: i rekao
• reported clause with da
• future with će + infinitive
• perfective verb for completed future action: pokositi
• agreement in svu travu

So it is a very good example sentence for several important parts of Croatian grammar.