A mi padre le gusta el ajo, pero no quiere demasiada pimienta.

Yes, they both point to the same person, but this is normal in Spanish.

This is called indirect object doubling:

• a mi padre names the person clearly
• le repeats that person with an indirect object pronoun

So:

• A mi padre le gusta el ajo = literally something like Garlic is pleasing to my father

In Spanish, with gustar, using le is standard, even when you also say a mi padre.

Without a mi padre, Le gusta el ajo is still correct, but it just means He/She likes garlic and depends on context.

Because the verb agrees with el ajo, which is singular.

With gustar, the thing being liked is the grammatical subject:

• el ajo = singular, so gusta
• las manzanas = plural, so gustan

Compare:

• A mi padre le gusta el ajo = My father likes garlic
• A mi padre le gustan los ajos = My father likes garlic cloves / kinds of garlic

So the verb does not agree with mi padre. It agrees with what causes the pleasure.

Gustar works differently from English to like.

English:

• My father likes garlic

Spanish structure:

• Garlic pleases my father
• A mi padre le gusta el ajo

So in this pattern:

• the person who likes something is an indirect object: a mi padre / le
• the thing liked is the subject: el ajo

That is why Spanish learners often need to mentally flip the structure.

The a is part of the indirect object phrase.

In A mi padre le gusta el ajo:

• a mi padre = to my father
• le = to him

This a is not the same as the personal a used with direct objects. Here it is simply introducing the person affected by gustar.

Spanish often uses the definite article when talking about things in a general sense, especially with verbs like gustar.

So:

• Me gusta el ajo = I like garlic
• No me gusta la carne = I don’t like meat
• Le encanta el chocolate = He/She loves chocolate

In English, we often drop the article:

• I like garlic
• not usually I like the garlic in the general sense

But in Spanish, the article is very natural here.

Because quiere and gusta mean different things.

• le gusta = he likes
• quiere = he wants

So the sentence means:

• he likes garlic
• but he does not want too much pepper

This suggests that he may be okay with some pepper, just not a lot.

If you said:

• A mi padre no le gusta demasiada pimienta

that would sound more like:

• My father doesn’t like too much pepper or
• My father doesn’t like a lot of pepper

That is close in meaning, but not exactly the same idea as doesn’t want too much pepper.

Because quiere works like a normal verb here, and mi padre is its subject.

In the second part:

• (mi padre) no quiere demasiada pimienta
• my father is the one doing the wanting

So no indirect object pronoun is needed.

Compare the two structures:

With gustar:

• A mi padre le gusta el ajo
• literally: Garlic pleases my father

With querer:

• Mi padre no quiere demasiada pimienta
• literally: My father does not want too much pepper

Different verb structure, so different grammar.

Because demasiada agrees with pimienta, which is a feminine singular noun.

• pimienta = feminine singular
• so the quantifier is demasiada

Examples:

• demasiado ajo = too much garlic
• demasiada pimienta = too much pepper
• demasiados tomates = too many tomatoes
• demasiadas cebollas = too many onions

So demasiado changes form like an adjective when it modifies a noun.

Because after quantity words like demasiado/a, Spanish normally does not use the article.

So:

• demasiada pimienta = too much pepper
• mucha sal = a lot of salt
• poco azúcar = little sugar

Using la here would sound unnatural in this context:

• not demasiada la pimienta

The quantifier already determines the noun, so no article is needed.

It can be reordered, although the original is very natural.

For example:

• A mi padre le gusta el ajo, pero no quiere demasiada pimienta.
• Le gusta el ajo a mi padre, pero no quiere demasiada pimienta.
• El ajo le gusta a mi padre, pero no quiere demasiada pimienta.

These alternatives are grammatically possible, but they may sound more marked or emphatic.

The original version is probably the most neutral and natural for everyday speech.

No. That is not correct in standard Spanish.

Because gustar does not work like English to like, you cannot normally say:

• Mi padre gusta el ajo

You need the gustar structure:

• A mi padre le gusta el ajo

A good rule is:

• person who likes = me / te / le / nos / os / les
• thing liked = subject of gustar

Yes. El ajo here means garlic as a substance or food in general.

Spanish often uses the singular for foods or substances when speaking generally:

• el ajo = garlic
• la leche = milk
• el pan = bread

If you used the plural, it would usually suggest separate items, types, or cloves:

• los ajos

So el ajo is the natural choice for the general idea of garlic.

Yes, pero simply means but.

It connects two contrasting ideas:

• he likes garlic
• but he does not want too much pepper

So it shows a contrast between:

• something he enjoys
• a limit or preference he has

It is a very common coordinating conjunction in Spanish, used much like English but.