Mi profesora me ayuda a pronunciar mejor las palabras difíciles.

Mi without an accent is the possessive adjective meaning my.

• mi profesora = my teacher

Mí with an accent is a pronoun used after a preposition:

• para mí = for me
• a mí = to me

So here, because it is directly describing profesora, you need mi.

Profesora is the feminine form of profesor.

• mi profesora = my female teacher
• mi profesor = my male teacher

In Spain, profesor/profesora is very common for teacher, especially in secondary school and higher education. Maestra is also possible, but it is more associated with primary school or with a more specific type of teacher. In this sentence, profesora is completely natural.

Me means me, and here it is the object pronoun.

• Mi profesora me ayuda = My teacher helps me

In Spanish, unstressed object pronouns usually go before a conjugated verb:

• me ayuda
• te ayuda
• nos ayuda

You usually attach them to the end only with:

• an infinitive: ayudarme
• a gerund: ayudándome
• an affirmative command: ayúdame

So in this sentence, me ayuda is the normal position.

Because ayudar is commonly followed by a + infinitive.

• ayudar a hacer algo = to help to do something
• me ayuda a pronunciar = she helps me pronounce / helps me to pronounce

So a is part of the normal structure after ayudar in standard Spanish.

After ayudar a, Spanish normally uses the infinitive to express the action being helped.

So:

• me ayuda a pronunciar
• literally: helps me to pronounce

This is very similar to English help someone do something or help someone to do something.

Mejor means better, and here it works as an adverb modifying pronunciar.

• pronunciar mejor = to pronounce better

It does not describe a noun here, so it does not change form.

A useful comparison:

• bien = well
• mejor = better

So the sentence is talking about improvement, not just doing it well.

Because it most clearly modifies the action pronunciar.

• pronunciar mejor las palabras difíciles = to pronounce difficult words better

If you move mejor, the sentence may still be understandable, but the rhythm and emphasis change. The original order sounds natural and clear.

Spanish often uses the definite article more than English does.

So las palabras difíciles is a very natural way to say:

• the difficult words
• or, in context, difficult words

Without las, the phrase can still be possible in some contexts, but this full version sounds more complete and natural in a normal statement like this one.

In Spanish, descriptive adjectives usually come after the noun.

So:

• palabras difíciles = difficult words

That is the normal order. Putting the adjective before the noun is much less common here and would sound marked, literary, or emphatic.

Because the adjective has to agree with the noun.

• palabra difícil = difficult word
• palabras difíciles = difficult words

Since palabras is plural, difícil becomes difíciles.

The accent mark stays in difíciles to keep the stress in the right place.

A rough guide for Spain would be:

Mi pro-fe-SO-ra me a-YU-da a pro-nun-thiar me-HOR las pa-LA-bras di-FI-ci-les

A few key points:

• In most of Spain, c before i sounds like th in think, so pronunciar sounds like pro-nun-thiar.
• The j in mejor is a strong throaty sound, not like the English j.
• profesora is stressed on so.
• difíciles is stressed on fí.

If you are learning Peninsular Spanish, that th sound in pronunciar is one of the main pronunciation features to notice.