La reĝisoro faris bonan filmon.

La is the definite article, meaning the.

So la reĝisoro means the director, not just a director.

A very important Esperanto point:
Esperanto has no indefinite article. There is no separate word for a/an.

So:

• reĝisoro = a director or just director
• la reĝisoro = the director

Yes. Reĝisoro is a normal Esperanto noun meaning director (especially of a film, play, etc.).

Like most Esperanto nouns, it ends in -o:

• reĝisoro = director
• filmo = film

The word is borrowed in an Esperanto-style form, which is very common in the language.

Faris is the past tense of fari, which means to do or to make.

Esperanto verb endings are very regular:

• fari = to do / to make
• faras = does / is doing / makes / is making
• faris = did / made
• faros = will do / will make

So La reĝisoro faris... means The director made... or The director did..., depending on context. Here, with filmon, it clearly means made a film.

Yes. Esperanto fari often covers both English verbs do and make.

For example:

• fari laboron = do work
• fari filmon = make a film
• fari eraron = make an error / make a mistake

So in this sentence, faris filmon is naturally understood as made a film.

Because filmon is the direct object, and in Esperanto the direct object takes -n.

Also, adjectives must agree with the noun they describe. So if the noun gets -n, the adjective gets -n too.

Breakdown:

• filmo = film
• filmon = film as a direct object
• bona filmo = a good film
• bonan filmon = a good film as a direct object

So:

• La reĝisoro faris bonan filmon.
• The director made a good film.

The -n on bonan and filmon shows that good film is what was made.

Yes, in this sentence it would be wrong.

Because the film is the thing being made, it is the direct object, so it must be:

• bonan filmon

not

• bona filmo

Without the -n, the grammar would not match the role of the noun phrase in the sentence.

In Esperanto, adjectives usually come before the noun, just like in English:

• bona filmo = good film

But they can also come after the noun:

• filmo bona

That is less neutral and may sound more literary, emphatic, or stylistically marked.

So bonan filmon is the normal, straightforward order.

Yes, Esperanto word order is fairly flexible because endings show the grammar.

For example, these all mean basically the same thing:

• La reĝisoro faris bonan filmon.
• Bonan filmon faris la reĝisoro.
• Faris la reĝisoro bonan filmon.

However, the first version is the most neutral and standard.

Because bonan filmon has -n, we know it is the object no matter where it appears.

Because Esperanto normally does not use an indefinite article.

So:

• filmo can mean a film
• filmon can mean a film as an object

In this sentence, bonan filmon naturally means a good film.

If Esperanto uses la, it means the. If there is no article, the noun is often indefinite or general.

A helpful approximation is:

reh-zhi-SO-ro

Key points:

• ĝ sounds like the j in judge
• the stress in Esperanto is always on the second-to-last syllable

So:

• re-ĝi-so-ro

with the stress on so.

Not always strictly a film director, but that is a very natural interpretation here because the sentence also says faris ... filmon.

Reĝisoro can refer to a director in film, theater, and similar contexts.
In this sentence, since the person made a film, director is the obvious meaning.

Normally, no. As written, bonan filmon is most naturally a good film, not the good film.

If you wanted the good film, you would usually say:

• la bonan filmon

So:

• bonan filmon = a good film
• la bonan filmon = the good film

It follows a very common pattern:

Subject + verb + object

• La reĝisoro = subject
• faris = verb
• bonan filmon = direct object

So the sentence is built in a very straightforward way:

The director + made + a good film