Čim se vrijeme razvedri, moja sestra pravi limunadu i nosi je na balkon.

Čim means as soon as. It introduces something that happens immediately after another thing.

• Čim se vrijeme razvedri... = As soon as the weather clears up...
• Kad se vrijeme razvedri... would be more like when the weather clears up

So čim is a bit more immediate than kad.

Here razvedriti se is a reflexive verb meaning to clear up when talking about the weather.

So:

• vrijeme se razvedri = the weather clears up

The se is part of the verb, not a separate word with its own meaning here. Many Croatian verbs use se in ways that do not translate literally into English.

In Croatian, vrijeme can mean both:

• time
• weather

The meaning depends on context. In this sentence, because of the verb razvedri se (clears up), it clearly means weather.

Croatian often uses the present tense after words like čim, kad, ako, and similar conjunctions, even when English would use a future idea.

So Croatian says:

• Čim se vrijeme razvedri...
  literally: As soon as the weather clears up...

Even though the event is in the future, the present tense is normal here.

It is from the perfective verb razvedriti se.

That matters because after čim, Croatian often uses a perfective present form to talk about a single completed event in the future:

• kad / čim se razvedri = when / as soon as it clears up

This present form does not mean a regular ongoing present in the usual sense. It refers to a future completed action.

Moja sestra means my sister.

Croatian does not always need possessives as often as English does, because context can make ownership clear. But using moja is completely natural here and simply makes it explicit.

So:

• moja sestra = my sister
• sestra could sometimes be enough if the context already makes it obvious whose sister is meant

Here pravi is the verb praviti = to make.

So:

• pravi limunadu = makes lemonade

This is different from the adjective pravi, which can mean real, true, or proper.

Compare:

• On pravi limunadu. = He makes lemonade.
• To je prava limunada. = That is real/proper lemonade.

Same form on the surface, but different grammar and meaning.

Normally, praviti is the clearer choice for to make in this sentence.

• praviti limunadu = to make lemonade

The verb raditi usually means to work or to do, although in some regional or colloquial usage people may use it more broadly. For a learner, praviti limunadu is the safest and most standard choice here.

Because limunadu is in the accusative case, which is used for the direct object.

• nominative: limunada
• accusative: limunadu

Since the sister is making lemonade, lemonade is the thing being made, so Croatian uses the accusative:

• pravi limunadu

Je here means it. It is the unstressed accusative pronoun referring back to limunadu.

So:

• nosi je na balkon = she carries/takes it to the balcony

Because limunada is feminine singular, the pronoun is je.

Because je is a clitic, an unstressed pronoun. Croatian clitics usually appear in the second position of their clause.

In the clause:

• i nosi je na balkon

the conjunction i does not count as the first real stressed element, so nosi comes first and the clitic je follows it.

That is why nosi je sounds natural, while i je nosi would not be the normal word order here.

Croatian uses na with places understood as surfaces, open areas, or places you go out onto, and balkon is treated that way.

So:

• na balkon = onto / to the balcony

By contrast, u is more like into/in for enclosed spaces.

Also notice the case:

• after na with motion, Croatian uses the accusative
• balkon is masculine inanimate, and its accusative singular is the same as the nominative singular

So:

• nominative: balkon
• accusative: balkon

Because the sentence begins with a subordinate clause:

• Čim se vrijeme razvedri, ...

Croatian normally separates that introductory clause from the main clause with a comma, just as English does in sentences like:

• As soon as the weather clears up, my sister...

Yes, Croatian word order is fairly flexible, but not completely free. This sentence could be rearranged for style or emphasis, for example:

• Moja sestra čim se vrijeme razvedri pravi limunadu i nosi je na balkon.

However, the original version is very natural because it sets up the time condition first:

• Čim se vrijeme razvedri, moja sestra pravi limunadu i nosi je na balkon.

So yes, word order can change, but the original is a very normal and clear choice.

They are ordinary present-tense forms, but in a sentence like this they often express a habitual or typical action.

So the meaning is something like:

• Whenever / as soon as the weather clears up, my sister makes lemonade and takes it to the balcony.

This is not necessarily one single event happening right now. It can describe what she typically does under those circumstances.