Yo no escribiría ochocientas palabras sobre esa película, pero sí leería una tercera reseña si fuera buena.

Yes, yo is usually optional in Spanish because the verb ending already shows the subject.

Here, yo adds emphasis or contrast. It helps underline the idea of I personally not doing one thing, even though I would do another:

• Yo no escribiría...
• ...pero sí leería...

So it sounds a bit like:

• I wouldn’t write 800 words about that film, but I would read a third review...

Without yo, the sentence would still be completely correct:

• No escribiría ochocientas palabras sobre esa película, pero sí leería una tercera reseña si fuera buena.

Both are in the conditional tense. In this sentence, they mean would write and would read.

• escribiría = I would write
• leería = I would read

The conditional is used here because the speaker is talking about a hypothetical attitude or action, not something they are actually doing right now.

So:

• No escribiría... = I wouldn’t write...
• Sí leería... = I would read...

Pero sí creates a strong contrast:

• pero = but
• sí = yes / indeed / actually

In this sentence, sí does not simply mean yes by itself. It is being used to reinforce the contrast with the previous negative statement:

• Yo no escribiría... pero sí leería...

This is like saying:

• I wouldn’t write..., but I would read...
• or more emphatically: I wouldn’t write..., but I definitely would read...

The sí helps correct or balance the negative idea before it.

Because sí with an accent is different from si without an accent.

• sí = yes / indeed
• si = if

In this sentence, both forms appear:

• pero sí leería = but I would indeed read
• si fuera buena = if it were good

This is a very common point of confusion, so the accent matters a lot.

Because after si in hypothetical sentences, Spanish normally uses the imperfect subjunctive, not the conditional.

So Spanish says:

• si fuera buena = if it were good

Not:

• si sería buena ❌

This is a key pattern:

• Si + imperfect subjunctive, then conditional

So here:

• si fuera buena → leería

This is the same structure as:

• Si tuviera tiempo, iría. = If I had time, I would go.
• Si fuera más barata, la compraría. = If it were cheaper, I would buy it.

Yes. Fuera and fuese are both correct imperfect subjunctive forms of ser.

So these are both correct:

• si fuera buena
• si fuese buena

In modern everyday Spanish, fuera is generally more common in speech, including in Spain. Fuese can sound a bit more formal or literary in some contexts, but it is not wrong at all.

It means a third review.

Here, tercera is an ordinal number:

• primera = first
• segunda = second
• tercera = third

So una tercera reseña means the speaker has in mind reading another review, specifically a third one.

It does not necessarily mean the third review in existence. In context, it usually means something like:

• a third review (after already having read two)

Because buena agrees with reseña, which is a feminine noun.

• reseña is feminine
• so the adjective must also be feminine:
  • una reseña buena
  • si fuera buena

Even though película is also feminine, here buena refers to reseña, not to película.

The idea is:

• I would read a third review if it were good not
• if the film were good

If the speaker meant the film, they would more likely say:

• si la película fuera buena

Because palabras is feminine plural, and ochocientas must agree with it.

• ochocientos = eight hundred (masculine)
• ochocientas = eight hundred (feminine)

So:

• ochocientas palabras = eight hundred words

Compare:

• ochocientos libros = eight hundred books
• ochocientas páginas = eight hundred pages

This agreement happens with cientos numbers in Spanish.

Here sobre means about.

So:

• escribir ... sobre esa película = to write ... about that film

This is a very common use of sobre when talking about the topic of writing or speaking.

Examples:

• un libro sobre historia = a book about history
• hablar sobre política = to talk about politics

Sometimes yes, but sobre is the most straightforward choice for about in this context.

• escribir sobre una película = to write about a film

Using de can sometimes work depending on the wording, but it is less directly equivalent here. For a learner, escribir sobre... is the safest and most natural pattern to remember.

They are similar, but not always identical.

• reseña usually means a review or write-up
• crítica can also mean review, but it can sound more like a critical evaluation, especially in film, art, or literature

In many contexts they overlap. In Spain, reseña is a very normal word for a written review. Crítica is also common, especially for more formal or professional criticism.

So una tercera reseña sounds natural.

Because the sentence is not describing a real present action or a definite future action. It is describing a hypothetical reaction.

The speaker is saying what they would and wouldn’t do under certain imagined circumstances:

• I wouldn’t write...
• but I would read...
• if it were good

That is exactly the kind of meaning Spanish often expresses with:

• conditional for the result
• imperfect subjunctive after si for the condition

Yes, that is grammatically correct, but it changes the nuance slightly.

• si fuera buena = if it were good
• si fuera una buena reseña = if it were a good review

The original version is more natural and concise because reseña has already been mentioned, so Spanish does not need to repeat it.

Yes. It is a very standard pattern:

• Si + imperfect subjunctive + conditional

In this sentence:

• si fuera buena = if it were good
• leería = I would read

This is one of the most important Spanish structures for unreal or unlikely situations in the present or future.

A good model to remember is:

• Si tuviera dinero, compraría el coche.
• Si fuera más interesante, la vería otra vez.
• Si fuera buena, leería una tercera reseña.