Kad mehaničar popravi kočnice, moći ćemo opet ići na more.

This is a very common Croatian pattern. After time words like kad (when), Croatian often uses the present tense of a perfective verb to talk about a future completed action.

So:

Kad mehaničar popravi kočnice...
literally looks like When the mechanic fixes the brakes...

but it really means:

When the mechanic has fixed / fixes the brakes...

English and Croatian handle this differently, but the Croatian sentence is completely normal.

Because popraviti is a perfective verb: it focuses on the action as completed. That fits the meaning here, because the next action happens after the brakes are fixed.

Compare:

• Kad mehaničar popravi kočnice... = When the mechanic fixes/has fixed the brakes...
• Kad mehaničar popravlja kočnice... = When the mechanic is repairing the brakes...

So popravi is about the repair being finished; popravlja is about the repair being in progress.

This is the future tense of moći (to be able / can):

• moći ću = I will be able
• moći ćeš = you will be able
• moći će = he/she/it will be able
• moći ćemo = we will be able

So moći ćemo means we will be able.

A useful spelling point: with verbs ending in -ći, Croatian keeps the infinitive separate from ću, ćeš, će, ćemo..., so you write moći ćemo, ići ću, etc.

Because after a modal verb like moći, Croatian normally uses the infinitive.

So:

• moći ćemo ići = we will be able to go

not:

• moći ćemo idemo

English does the same kind of thing: we will be able to go, not we will be able we go.

In standard Croatian, after moći you normally use the infinitive directly:

• moći ćemo ići

not:

• moći ćemo da idemo

That da + present tense pattern is much more associated with Serbian and some regional speech, but it is not the standard Croatian choice here.

It is the direct object, so it is in the accusative plural.

The base noun is kočnica (brake). In the plural:

• nominative plural: kočnice
• accusative plural: kočnice

So in this sentence, the form happens to look the same as the nominative plural.

Because for a car, you normally talk about the brakes as a set, just as in English. Croatian often uses the plural here naturally:

• popraviti kočnice = fix the brakes

You could talk about one brake in the singular if you specifically meant one individual part, but in everyday use the plural is the normal choice.

Because na more is the normal Croatian expression for going to the seaside / going to the coast / going on a seaside holiday.

• ići na more = go to the seaside
• u more = into the sea

So na more does not mean physically onto the sea; it is just the idiomatic expression Croatian uses.

Opet means again. Here it shows that going to the seaside is something the speakers used to be able to do before, and they expect to do it once more after the brakes are fixed.

So the feeling is:

we’ll be able to go to the seaside again

Yes, Croatian word order is fairly flexible. You can move opet around a bit, depending on what you want to emphasize.

For example:

• moći ćemo opet ići na more
• opet ćemo moći ići na more

Both are natural. The meaning stays very similar, but the emphasis shifts slightly.

Because Croatian often leaves subject pronouns out when the verb already makes the subject clear. The ending -mo in ćemo already tells you it is we.

So:

• moći ćemo already means we will be able

You could add mi (we) for emphasis, but it is not necessary.

This sentence has both:

• kočnice has č
• moći ćemo has ć

A simple learner-friendly guide:

• č is a harder ch sound, roughly like ch in church
• ć is softer; many English speakers approximate it with something like a very soft ty/ch sound

You do not need a perfect native distinction at first, but it is good to notice that Croatian treats č and ć as different sounds and different letters.