Jakmile budeme v novém bytě, pozvu sousedku na kávu.

Jakmile means as soon as or once. It introduces a time clause:

• Jakmile budeme v novém bytě = As soon as we are in the new apartment

It suggests that one action will happen immediately after another.

Because Jakmile budeme v novém bytě is a subordinate clause, and Czech normally separates subordinate clauses from the main clause with a comma.

So the structure is:

• subordinate clause: Jakmile budeme v novém bytě
• main clause: pozvu sousedku na kávu

This is very standard Czech punctuation.

Because the sentence refers to the future.

• jsme = we are
• budeme = we will be

So:

• Jakmile jsme v novém bytě would sound wrong here, because it would not match the future meaning.
• Jakmile budeme v novém bytě = As soon as we are / will be in the new apartment

In English, after as soon as, we often use a present form with future meaning: As soon as we are in the new apartment... Czech can also use a future form here.

Because v here means in, showing location, and location after v takes the locative case.

So:

• byt = apartment
• v bytě = in the apartment

The adjective has to match too:

• nový byt = a new apartment
• v novém bytě = in the new apartment

So both words change because of the locative case.

It is the locative singular.

Breakdown:

• byt is a masculine inanimate noun
• nominative: nový byt
• locative after v: v novém bytě

The adjective nový changes to novém to agree with bytě.

Pozvu is the correct form because pozvat is a perfective verb.

In Czech, perfective verbs use present-tense forms to express the future:

• pozvu = I will invite

So although the form looks present-like, the meaning is future.

You do not say budu pozvat.
With perfective verbs, that construction is not used.

They come from different aspects:

• zvat / zvu = imperfective, ongoing or repeated inviting
• pozvat / pozvu = perfective, a single completed invitation

In this sentence, the speaker means one future act:

• I’ll invite the neighbor for coffee

So pozvu is the natural choice.

Sousedku is the accusative singular of sousedka, which means female neighbor.

• nominative: sousedka
• accusative: sousedku

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

• pozvu koho? = I will invite whom?
• sousedku

So the sentence specifically refers to a female neighbor.

After pozvat, Czech often uses na + accusative to mean invite someone for/to food, drink, or an activity.

Examples:

• pozvat na kávu = invite for coffee
• pozvat na oběd = invite for lunch
• pozvat na večeři = invite for dinner

So na kávu is a very normal Czech expression.

Because the preposition na often takes the accusative when it expresses purpose, destination, or going/inviting someone for something.

Here it is part of the pattern:

• pozvat někoho na něco = to invite someone for something

So:

• káva = coffee
• na kávu = for coffee

Yes, very often you could.

• jakmile = as soon as
• až = when / once / by the time, depending on context

In this sentence:

• Jakmile budeme v novém bytě, pozvu sousedku na kávu.
• Až budeme v novém bytě, pozvu sousedku na kávu.

Both are possible.
Jakmile sounds a bit more clearly like immediately once that happens.

Yes. Czech word order is flexible, although each version can sound slightly different in emphasis.

For example, you could also say:

• Pozvu sousedku na kávu, jakmile budeme v novém bytě.

This puts the main action first and the time condition second.

The original version is very natural because it sets up the time frame first.

Because Czech usually leaves subject pronouns out when the verb ending already shows who the subject is.

• budeme already means we will be
• pozvu already means I will invite

So adding pronouns is usually unnecessary unless you want emphasis or contrast.

For example:

• Jakmile budeme v novém bytě, já pozvu sousedku na kávu.

This would sound more emphatic, like I will invite her.

It can mean either, depending on context.

• brand-new apartment
• new apartment in the sense of our new place

Without extra context, Czech nový byt is just like English new apartment and can mean either one.