Ojalá las avispas no se acercaran a la comida, porque mi prima les tiene bastante miedo.

Ojalá expresses a wish, hope, or strong desire, something like I wish, hopefully, or if only.

In Spanish, ojalá is normally followed by the subjunctive, because it introduces something wished for rather than something presented as a fact.

So:

• Ojalá... = I wish... / If only...

In this sentence, the speaker is expressing a wish about the wasps staying away from the food.

Because after ojalá, Spanish uses the subjunctive, not the indicative.

• se acercan = indicative, they come near / they approach
• se acercaran = imperfect subjunctive, used here after ojalá

The indicative would sound wrong here because the speaker is not describing a fact; they are expressing a wish.

So:

• Ojalá las avispas no se acercaran... = correct
• Ojalá las avispas no se acercan... = incorrect

This is a very common question. After ojalá, the tense of the subjunctive changes the nuance.

Ojalá + present subjunctive

Used for a wish that feels more possible or more open in the present/future.

• Ojalá las avispas no se acerquen a la comida.
  I hope the wasps don’t come near the food.

Ojalá + imperfect subjunctive

Used for a more hypothetical, less likely, or more emotionally distanced wish; often like I wish they wouldn’t...

• Ojalá las avispas no se acercaran a la comida.

So in your sentence, se acercaran gives a slightly more resigned or hypothetical feeling, as if the speaker sees this as difficult to control.

Yes. That would also be correct, but the nuance changes slightly.

• Ojalá... no se acerquen... = I hope they don’t come near the food
• Ojalá... no se acercaran... = I wish they wouldn’t come near the food / If only they stayed away

The version with imperfect subjunctive often sounds a bit more wistful, less optimistic, or more hypothetical.

Yes, here the verb is acercarse a, which means to go near, to come close to, or to approach.

So:

• acercar = to bring something closer
  
  • Acercó la silla a la mesa. = He moved the chair closer to the table.
• acercarse a = to approach / to come near
  
  • Las avispas se acercan a la comida. = The wasps approach the food.

The se is part of the verb acercarse in this meaning.

Because the verb pattern is acercarse a algo/alguien = to approach something/someone.

So the preposition a is required:

• acercarse a la comida
• acercarse al fuego
• acercarse a una persona

It is just part of the verb construction, not the personal a.

Les refers to las avispas.

So the idea is:

• Mi prima les tiene bastante miedo
  = My cousin is quite afraid of them
• them = the wasps

Even though mi prima is singular, les is plural because it refers to the wasps, not to the cousin.

Because with tener miedo (a), Spanish commonly uses le/les to refer to the person or animal feared.

So you get:

• Le tengo miedo a ese perro.
• Les tengo miedo a las avispas.

Even though English speakers may expect a direct-object pronoun like las, Spanish normally uses le/les in this pattern.

This is something you should mostly learn as a set expression:

• tenerle miedo a alguien/algo
• tenerles miedo a...

Yes, absolutely.

That version is completely natural:

• Mi prima tiene bastante miedo a las avispas.

The version in your sentence uses les to refer back to las avispas, which avoids repeating the noun.

So both are possible:

• Mi prima tiene bastante miedo a las avispas.
• Mi prima les tiene bastante miedo.

You can even hear both together for emphasis or clarity:

• Mi prima les tiene bastante miedo a las avispas.

Here bastante means quite, rather, or fairly.

So:

• tener bastante miedo = to be quite afraid / fairly scared

It softens the statement a little compared with something stronger like:

• mucho miedo = a lot of fear / very afraid

Compare:

• Mi prima les tiene bastante miedo. = My cousin is quite afraid of them.
• Mi prima les tiene mucho miedo. = My cousin is very afraid of them.

Because bastante is modifying the noun miedo.

• bastante miedo = quite a lot of fear

This is the normal word order in Spanish:

• mucho miedo
• bastante miedo
• demasiado miedo

So les tiene bastante miedo is the expected order.

No. You can also say se acercasen.

Both are correct imperfect subjunctive forms:

• Ojalá las avispas no se acercaran...
• Ojalá las avispas no se acercasen...

In modern Spanish, both are grammatical. In everyday use, the -ra form is usually more common, so acercaran will often sound more natural to many speakers.

Because ojalá can be used with or without que.

So both are possible:

• Ojalá las avispas no se acercaran a la comida.
• Ojalá que las avispas no se acercaran a la comida.

The meaning does not really change. The version without que is very common.

Because porque here means because and introduces the reason.

• porque = because
• por qué = why

So:

• ..., porque mi prima les tiene bastante miedo.
  = ..., because my cousin is quite afraid of them.

If it were a question, then you would use por qué:

• ¿Por qué les tiene miedo? = Why is she afraid of them?