Kiam la pordo ne bone fermiĝas, lerta laboristino povas ripari ĝin en kelkaj minutoj.

Kiam means when and introduces a time clause. In this sentence, Kiam la pordo ne bone fermiĝas sets up the situation first, and then the main clause tells what can happen next.

So the structure is:

• Kiam ... = when ...
• main clause = what happens in that situation

The part beginning with kiam is a subordinate clause, and Esperanto normally separates it from the main clause with a comma.

So:

• Kiam la pordo ne bone fermiĝas = subordinate clause
• lerta laboristino povas ripari ĝin en kelkaj minutoj = main clause

This is very similar to English when a when-clause comes first.

It comes from:

• fermi = to close something
• -iĝ- = to become, to get into a state

So fermiĝi means to become closed, to close, or to get shut.

That is why fermiĝas is different from fermas:

• La virino fermas la pordon = The woman closes the door
• La pordo fermiĝas = The door closes / is getting closed

Here it describes what the door does, not what someone does to it.

Because bone is an adverb, and adverbs in Esperanto end in -e.

It modifies the verb fermiĝas, telling us how the door closes.

• bona = good, as an adjective describing a noun
• bone = well, as an adverb describing a verb

So:

• bona pordo = a good door
• bone fermiĝas = closes well

Both are possible, but they are slightly different in tone.

• ne bone = not well, not properly
• malbone = badly

In this sentence, ne bone sounds a bit more natural if the idea is that the door does not function as it should. It suggests a problem without sounding as strong as badly.

La means the, so la pordo refers to a specific door.

But lerta laboristino means a skilled female worker in a general, indefinite sense. Esperanto has no indefinite article, so where English uses a or an, Esperanto usually uses nothing.

So:

• la pordo = the door
• lerta laboristino = a skilled female worker

The word breaks down like this:

• labori = to work
• laboristo = worker
• laboristino = female worker

The suffix -in- marks the female form.

So:

• patro = father
• patrino = mother
• instruisto = teacher
• instruistino = female teacher

In modern Esperanto, some speakers use the basic form when gender is not important, and the feminine form when they specifically want to show female gender.

Because adjectives in Esperanto end in -a, and they agree with the noun they describe.

Here:

• lerta describes laboristino
• both are singular
• both are in the basic form, not accusative

So lerta stays -a.

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

• lertaj laboristinoj = skilled female workers

If it were accusative too, both would take -n:

• Mi vidas lertan laboristinon = I see a skilled female worker

In Esperanto, only the first verb is conjugated here.

• povas = can
• ripari = to repair

After verbs like povi, the next verb normally stays in the infinitive.

So this pattern is very common:

• mi volas iri = I want to go
• ŝi povas helpi = she can help
• ili devas atendi = they must wait

So povas ripari is exactly what you would expect.

Ĝi means it, and ĝin is the accusative form.

The -n shows that it is the direct object of ripari. It refers back to la pordo.

So:

• ĝi = it
• ĝin = it, as a direct object

Compare:

• La pordo estas peza. Ĝi estas malnova. = The door is heavy. It is old.
• La laboristino riparas ĝin. = The worker repairs it.

Esperanto often uses a pronoun just as English does, to avoid unnecessary repetition.

So instead of saying:

• ... povas ripari la pordon ...

the sentence says:

• ... povas ripari ĝin ...

That sounds smoother and more natural once the door has already been mentioned.

En kelkaj minutoj means in a few minutes or within a few minutes.

The preposition en here shows the time needed for the action to be completed.

• en kelkaj minutoj = within a few minutes
• dum kelkaj minutoj = for a few minutes

That is an important difference:

• ripari ĝin en kelkaj minutoj = finish repairing it within a few minutes
• ripari ĝin dum kelkaj minutoj = spend a few minutes repairing it

Also:

• kelkaj = a few, some
• minutoj = minutes

Since minutoj is plural, kelkaj is plural too.