Sube un poco el volumen, que la película no se oye bien.

Sube is the affirmative tú command of subir.

So Sube un poco el volumen means Turn the volume up a bit when speaking to one person informally.

Related forms:

• tú: sube
• usted: suba
• vosotros (Spain): subid
• ustedes: suban

So in Spain, if you were talking to several people informally, you would say Subid un poco el volumen.

Spanish often uses subir and bajar with things like el volumen, la música, la calefacción, etc.

So:

• subir el volumen = turn the volume up
• bajar el volumen = turn the volume down

This is very natural Spanish. Even though subir literally means to go up or to raise, with volumen it works just like English turn up.

Un poco means a little or a bit.

In Sube un poco el volumen, it softens the command and makes it sound less abrupt:

• Sube el volumen = Turn up the volume.
• Sube un poco el volumen = Turn up the volume a bit.

Its position is normal here. You may also hear:

• Sube el volumen un poco

Both are correct, though Sube un poco el volumen sounds very natural.

It is el volumen because volumen is the direct object of sube.

You are raising the volume, so no a is needed:

• Sube el volumen = Raise the volume.

You would use a only in other grammatical situations, not here.

Spanish also often prefers the definite article where English might use a possessive or leave it more general. In context, el volumen clearly means the volume of the TV / film / device.

Here que means something like because, since, or it’s just that.

So:

• Sube un poco el volumen, que la película no se oye bien. means:
• Turn the volume up a bit, because the film can’t be heard well.

This use of que is very common in everyday Spanish, especially after a request, command, or suggestion.

It often sounds a bit more conversational and immediate than porque.

Yes, you could say:

• Sube un poco el volumen, porque la película no se oye bien.

That is grammatically correct and easy to understand.

But in everyday speech, especially in Spain, que is very common after commands when giving the reason:

• Ven, que ya es tarde.
• Date prisa, que perdemos el tren.

So in this sentence, que sounds very natural and colloquial.

Because la película is the thing being heard, not the person doing the hearing.

• no oye bien would usually mean he/she doesn’t hear well
• no se oye bien means it can’t be heard well / it doesn’t come through clearly

Here se oye is a very common Spanish way to talk about how something sounds or whether it can be heard:

• No se oye nada. = You can’t hear anything.
• ¿Se oye bien? = Can you hear it well? / Does it sound clear?

So la película no se oye bien means the film’s audio is not coming through clearly.

For a learner, the most useful way to understand it here is:

• la película is the grammatical subject
• se oye bien means is heard well / can be heard well

So it behaves a lot like an English passive idea, even though Spanish often prefers this se construction instead of a full passive.

Compare:

• La película no se oye bien. = The film can’t be heard well.
• La película no es oída bien. = grammatically possible in theory, but unnatural

So this se structure is the normal, idiomatic choice.

Because the subject is la película, which is singular.

• la película → singular
• therefore se oye

If the subject were plural, the verb would change:

• Las películas no se oyen bien.

Here bien means well, but in context it often has the sense of:

• clearly
• properly
• loud enough

So no se oye bien does not necessarily mean the sound is completely absent. It can also mean:

• the volume is too low
• the audio is unclear
• the sound quality is poor

Yes. You could also say:

• Sube un poco el volumen, que la película no se escucha bien.

That is also natural.

Very roughly:

• oír = to hear
• escuchar = to listen

But in many real-life situations, especially with sound coming from a TV, phone, or film, both verbs can be used in this kind of sentence.

Still, no se oye bien is extremely common for audio problems.

It works in general Spanish, but it does sound very natural in Spain.

A few points that fit Spain especially well:

• the use of tú command sube
• the very natural conversational que for because
• the overall phrasing

In Latin America, people would understand it perfectly too, though command forms and everyday preferences may vary depending on the country.

You could make it more polite by changing the command form or by turning it into a question.

Examples:

• Suba un poco el volumen, que la película no se oye bien.
  polite singular (usted)

• ¿Puedes subir un poco el volumen? Es que la película no se oye bien.
  softer, friendly

• ¿Podrías subir un poco el volumen?
  even more polite

So the original sentence is natural and normal, but it is fairly direct, as commands often are.