Apenaŭ ni subskribis, la luiganto transdonis la ŝlosilojn.

Here apenaŭ means something like hardly, scarcely, or more naturally in English, no sooner / as soon as in this kind of structure.

So:

Apenaŭ ni subskribis, la luiganto transdonis la ŝlosilojn.

means the second action happened almost immediately after the first one.

A very natural English equivalent is:

No sooner had we signed than the landlord handed over the keys.

or

As soon as we signed, the landlord handed over the keys.

Not in this sentence.

By itself, apenaŭ often does mean barely or hardly:

Mi apenaŭ aŭdas vin. = I can barely hear you.

But in the pattern Apenaŭ ..., ..., it often expresses immediate sequence:

Hardly had X happened, when Y happened.

So here it does not mean that signing almost failed. It means that once the signing was done, the landlord immediately gave the keys.

Esperanto often uses the ordinary past tense -is where English uses either signed or had signed.

The order of events is understood from context:

• first: ni subskribis
• then: la luiganto transdonis la ŝlosilojn

Because apenaŭ already shows that the first action happened just before the second one, Esperanto does not need a separate pluperfect form here.

So subskribis can correspond to English signed or had signed, depending on context.

Esperanto does not need an extra word here. The meaning of hardly had we signed, when... or no sooner had we signed than... is carried by apenaŭ plus the two clauses.

So the structure itself does the job:

• Apenaŭ ni subskribis, ...
• then the next clause follows.

English often wants a connector like when or than, but Esperanto can express the same idea without one.

Subskribis comes from:

• sub- = under
• skribi = to write
• -is = past tense

So literally it is wrote under, which corresponds to signed.

The infinitive is subskribi = to sign.

Examples:

• Mi subskribas. = I am signing / I sign.
• Mi subskribis. = I signed.

Luiganto means the person who rents something out, so here the landlord.

It is built from several parts:

• lu- = rent / lease
• -ig- = cause, make happen
• -ant- = active present participle, someone doing the action
• -o is understood in the noun ending form -anto

So luigi means to rent out or to let, and luiganto is one who rents out property.

That is why it refers to the landlord, not the tenant.

Esperanto often prefers words that are transparently built from roots and affixes.

So instead of having one completely separate root meaning landlord, Esperanto can say:

• luiganto = the one who rents out

This is very typical of Esperanto vocabulary. Once you know the pieces, many words become easier to understand.

Transdonis means handed over, passed over, or transferred.

It comes from:

• trans- = across, over
• doni = to give
• -is = past tense

So transdoni is stronger and more specific than just doni. It suggests giving something over from one party to another, often formally or as part of a process.

In this sentence, that fits very well: after the signing, the landlord handed over the keys.

Because ŝlosilojn is the direct object of transdonis.

The landlord handed over what?
la ŝlosilojn

In Esperanto, direct objects take -n.

Compare:

• La luiganto transdonis la ŝlosilojn.
• Mi vidas la domon.
• Ni subskribis la kontrakton.

Here:

• ŝlosilo = key
• ŝlosiloj = keys
• ŝlosilojn = keys as a direct object

Because the sentence refers to the keys, not the key.

That is often realistic in context: a property may have several keys, such as a front-door key, apartment key, mailbox key, gate key, and so on.

Grammatically:

• ŝlosilo = key
• ŝlosiloj = keys
• ŝlosilojn = keys as direct object

La is the definite article, meaning the.

It is used because these are specific, identifiable things in the situation:

• la luiganto = the landlord involved in this rental situation
• la ŝlosilojn = the keys for that property

English would also normally use the here, so this part matches English quite closely.

Esperanto word order is fairly flexible, but this sentence uses a very normal and natural order.

Current order:

• Apenaŭ ni subskribis,
• la luiganto transdonis la ŝlosilojn.

That is straightforward and easy to understand.

You could sometimes move things around for emphasis, but for a learner, this standard order is best. Since Esperanto marks the direct object with -n, meaning is often still clear even if word order changes, but the ordinary subject-verb-object order is the safest default.

Yes, the comma helps separate the two clauses:

• Apenaŭ ni subskribis
• la luiganto transdonis la ŝlosilojn

It makes the sentence easier to read and shows the break between the first action and the second.

Even when punctuation can vary a little in Esperanto, using a comma here is very natural and helpful.

Yes. A sentence with tuj kiam would also express that the second thing happened right after the first:

Tuj kiam ni subskribis, la luiganto transdonis la ŝlosilojn.

That means As soon as we signed, the landlord handed over the keys.

The difference is mostly in tone:

• apenaŭ gives a hardly had we... / no sooner... feeling
• tuj kiam is a more direct as soon as

Both are good, but apenaŭ sounds a little more literary or dramatic.