Se la raporto estos preta post unu horo, nia estro subskribos ĝin tuj.

Se means if. It introduces a condition:

Se la raporto estos preta post unu horo...
= If the report is ready in/after one hour...

So the second part of the sentence depends on that condition being true.

That is a very common question for English speakers.

In Esperanto, tense is usually chosen more directly by time. Since both actions are in the future, estos and subskribos are perfectly normal:

• estos = will be
• subskribos = will sign

So Esperanto does not have to follow the English pattern if + present, main clause + future. It can simply use the future in both parts when both events are future.

This is the normal Esperanto way to say will be ready:

• esti = to be
• estos = will be
• preta = ready

So:

• la raporto estas preta = the report is ready
• la raporto estos preta = the report will be ready

Preta is an adjective describing la raporto.

Because preta is an adjective describing la raporto.

• -a = adjective
• -e = adverb

So:

• preta = ready
• prete = ready/in a ready way, which would not fit here

It is also not preton, because there is no accusative needed here. The noun raporto is the subject of estos, not a direct object.

If the noun were plural, the adjective would also change:

• la raportoj estos pretaj = the reports will be ready

Because la raporto is the subject of the verb estos.

In Esperanto, -n marks the direct object, not the subject.

Here:

• la raporto = the thing that will be ready
• ĝin = the thing that the boss will sign

So the direct object appears later in the sentence, not here.

Because ĝin is the direct object of subskribos.

• ĝi = it
• ĝin = it (as a direct object)

The pronoun refers back to la raporto:

• nia estro subskribos ĝin = our boss will sign it

This is exactly the same accusative -n that nouns can take.

Because the possessive nia already makes the noun definite.

• estro = boss, chief, head
• nia estro = our boss

In Esperanto, when you use a possessive word like mia, via, nia, lia, and so on, you normally do not add la.

So nia estro is the normal form.

Literally, it means after one hour.

In this sentence, it means that one hour passes, and then the report will be ready.

So:

• post unu horo = after an hour / one hour later

English often says in an hour, but Esperanto learners should notice that post focuses on what happens after that interval has passed.

Not exactly.

A useful basic distinction is:

• post unu horo = after one hour has passed
• en unu horo = in one hour / within one hour / over the course of one hour, depending on context

In real usage, translation into English can sometimes overlap, but the core idea is different:

• post points to a moment after an interval
• en often points to the time within which something happens or the time it takes

So post unu horo is a natural choice here.

It comes from the verb subskribi, meaning to sign.

Esperanto verbs are very regular:

• subskrib- = verb stem
• -os = future tense

So:

• subskribi = to sign
• subskribas = signs / is signing
• subskribis = signed
• subskribos = will sign

There is no separate word for will. The ending -os already contains that meaning.

Tuj means immediately, right away, or at once.

Its position is quite natural at the end:

nia estro subskribos ĝin tuj
= our boss will sign it immediately

Esperanto word order is fairly flexible, so tuj could be moved for emphasis, but the version in the sentence is standard and clear.

Yes. Esperanto allows that very easily.

You could also say:

Nia estro subskribos ĝin tuj, se la raporto estos preta post unu horo.

That means the same thing:
Our boss will sign it immediately if the report is ready after/in one hour.

Putting the se-clause first is often a natural way to present the condition before the result.

Ĝ is pronounced like the j in job.

So ĝin is approximately jeen, with:

• ĝ = English j
• i = the vowel sound of machine
• n pronounced clearly at the end

So it is not like English gin with a short vowel. It is closer to jeen.