Na terasi pijemo kavu i gledamo kako trava raste poslije kiše.

Croatian normally uses na with places understood as open surfaces or open areas, and a terrace fits that pattern. So na terasi is the natural way to say on/at the terrace.

Compare:

• na balkonu = on the balcony
• na plaži = on the beach
• u sobi = in the room

So u terasi would not be the normal choice here.

Because after na meaning location, Croatian uses the locative case.

The base form is terasa. In the singular locative, it becomes terasi:

• terasa = terrace
• na terasi = on the terrace

A useful contrast:

• na terasi = on the terrace, already there
• na terasu = onto the terrace, movement toward it

Because kavu is the accusative singular form, and it is the direct object of pijemo.

The dictionary form is kava = coffee.
When it is the thing being drunk, it changes:

• kava → kavu

This is very common with feminine nouns ending in -a:

• voda → vodu
• knjiga → knjigu
• kava → kavu

It is built into the verb ending. In Croatian, subject pronouns are often omitted because the verb already shows who is doing the action.

Here:

• pijemo = we drink / we are drinking
• gledamo = we watch / we are watching

The ending -mo tells you the subject is we.
You could add mi for emphasis, but it is not necessary:

• Mi pijemo kavu = We are drinking coffee with extra emphasis on we

They are all in the present tense.

• pijemo = we drink / we are drinking
• gledamo = we watch / we are watching
• raste = grows / is growing

Croatian does not have a separate tense like the English am drinking / are watching / is growing form. The regular present tense often covers both the simple and continuous meaning, depending on context.

Because in Croatian, the present tense of an imperfective verb can describe an action happening right now.

That is exactly what is happening here:

• piti = to drink, imperfective
• gledati = to watch, imperfective
• rasti = to grow, imperfective

So pijemo kavu i gledamo kako trava raste naturally describes an ongoing scene. English often prefers are drinking and are watching, but Croatian does not need a special progressive form.

Because trava is grammatically singular. It works like a mass noun, just like English grass.

So:

• trava raste = the grass grows / is growing

Even though grass consists of many blades, Croatian treats trava as a singular noun in normal usage.

Here kako introduces a clause after a verb of perception, especially with verbs like gledati.

So:

• gledamo kako trava raste

means:

• we watch how the grass grows or more naturally in English,
• we watch the grass grow

So kako is not asking how? as a question here. It is linking the main verb gledamo to the action being observed.

Yes, and that is usually the most natural English translation.

A more literal version is:

• we watch how the grass grows

But in normal English, after watch, you usually say:

• watch the grass grow

So the Croatian structure with kako is normal, even if English often drops how in this kind of sentence.

Because poslije requires the genitive case.

The base form is kiša = rain.
After poslije, it becomes kiše:

• poslije kiše = after the rain

This is a standard preposition + case pattern in Croatian.

Yes. Nakon kiše and poslije kiše both mean after the rain.

In many contexts they are interchangeable:

• poslije kiše
• nakon kiše

A rough tendency:

• poslije is very common in everyday speech
• nakon can sound a little more neutral or formal

But both are correct standard Croatian.

Because Croatian has no articles. There is no direct equivalent of English a/an or the.

So:

• kavu can mean coffee or the coffee, depending on context
• trava can mean grass or the grass
• kiše can mean rain or the rain

The listener understands definiteness from the situation, word order, and context.

Yes. Croatian word order is fairly flexible because the endings show grammatical relationships.

The given sentence is neutral and natural:

• Na terasi pijemo kavu i gledamo kako trava raste poslije kiše.

But other orders are possible, for example:

• Pijemo kavu na terasi i gledamo kako trava raste poslije kiše.

That still means the same thing overall, but the emphasis changes a little.
Starting with Na terasi sets the scene first, which sounds very natural in this sentence.