Kad budem završila sve obaveze, sjest ću u fotelju, pojesti nekoliko trešanja i napokon se odmoriti.

Because after kad in a clause referring to the future, Croatian normally does not use Future I (ću + infinitive) the way English uses will.

Here, kad budem završila is a future-time clause meaning something like when I have finished / once I finish.

A very important contrast:

• Kad budem završila sve obaveze, ... = When I finish all my obligations, ...
• Kad ću završiti? = When will I finish?

So kad ću završiti usually sounds like a question (direct or indirect), not like the time clause in this sentence.

Yes. That is very natural and common.

So both of these can work:

• Kad završim sve obaveze, ...
• Kad budem završila sve obaveze, ...

The version with budem završila makes the idea of completion a bit more explicit: first I finish everything, and only then I do the next actions.

For a learner, it is useful to recognize both patterns.

Yes.

The form završila agrees with the subject in gender and number. So this sentence is being said by a female singular speaker: I (female) will have finished.

Compare:

• budem završila = said by a woman
• budem završio = said by a man

This same gender agreement appears in many Croatian verb forms built with the -l participle.

It is accusative plural.

Why? Because završiti takes a direct object, and direct objects are typically in the accusative.

So:

• obaveza = obligation, task
• obaveze = accusative plural here

And sve matches it:

• sve obaveze = all the obligations / all the tasks

For this noun, the nominative plural and accusative plural happen to look the same: obaveze.

Because in Croatian Future I, when the auxiliary ću comes after the infinitive, the infinitive usually drops its final -i.

So:

• sjesti + ću → sjest ću
• pojesti + ću → pojest ću

Compare the two word orders:

• Sjesti ću → normally contracted to Sjest ću
• Ja ću sjesti → the infinitive stays full because ću comes first

This is a very common pattern in Croatian.

Because Croatian often uses the auxiliary only once when several infinitives share the same subject and tense.

So this is completely normal:

• sjest ću u fotelju, pojesti nekoliko trešanja i napokon se odmoriti

The later verbs still belong to the same future meaning. In effect, the sentence means:

• I will sit down..., (I will) eat..., and (I will) finally rest.

You can repeat ću for emphasis or rhythm, but it is usually unnecessary and less elegant in a sentence like this.

Because sjesti means to sit down, which involves movement into a position. With movement toward/into something, Croatian often uses u + accusative.

So:

• sjesti u fotelju = to sit down into the armchair

But if you are already seated and talking about location, you use u + locative:

• sjediti u fotelji = to be sitting in the armchair

So the contrast is:

• sjesti u fotelju = movement/change of position
• sjediti u fotelji = location/state

Because nekoliko is a quantity word, and after words like that Croatian typically uses the genitive plural.

So:

• trešnja = cherry
• trešanja = genitive plural

Therefore:

• nekoliko trešanja = several cherries

This is the same pattern you see in many other phrases:

• mnogo ljudi = many people
• nekoliko knjiga = several books
• par minuta = a couple of minutes

Because the usual verb here is odmoriti se, meaning to rest / to get some rest.

In this meaning, se is part of the verb.

So:

• odmoriti se = to rest
• napokon se odmoriti = to finally get some rest

Without se, odmoriti is usually understood differently, often as a transitive idea such as to rest something:

• odmoriti noge = to rest one’s legs

So in your sentence, se is necessary.

Because pojesti is perfective and presents the action as a complete event.

That fits the structure of the sentence very well: after finishing all obligations, the speaker will then do a sequence of completed actions:

• sjest ću = I’ll sit down
• pojesti nekoliko trešanja = I’ll eat several cherries
• odmoriti se = I’ll rest

If you used jesti, the focus would be more on the ongoing activity of eating rather than on one completed step in the sequence.

So pojesti sounds very natural here.

Yes, they are all perfective (or used here in a perfective sense), and that matters a lot.

Perfective verbs present actions as whole, completed events. That is exactly what this sentence wants:

1. finish all obligations
2. sit down
3. eat some cherries
4. finally rest

This gives the sentence a clear step-by-step, one-time future sequence.

If you switched to imperfective verbs, the meaning would change:

• jesti = to be eating / to eat in a general or ongoing sense
• odmarati se = to be resting / rest habitually or over a period

So the perfective choices make the sentence sound like a neat plan of completed future actions.