No siempre comprendo la idea a la primera, pero la profesora la explica con calma.

Because no siempre is the natural way to say not always in Spanish.

• No siempre comprendo... = I don’t always understand...
• Siempre no is generally not how Spanish expresses this idea.

Putting no before siempre negates always, not the whole sentence in a strange way. So the meaning is:

• Sometimes I understand it, sometimes I don’t.

This is very similar to English not always.

Both comprender and entender can mean to understand, and in many contexts they are interchangeable.

In this sentence:

• comprendo la idea = I understand the idea
• entiendo la idea would also be correct

That said, learners often notice a slight nuance:

• entender is very common in everyday speech
• comprender can sound a little more formal, careful, or intellectual in some contexts

In Spain, both are normal, but entender may feel a bit more common in casual conversation.

Because comprendo is the first person singular form of the present tense.

The subject is understood to be I, so Spanish uses the conjugated verb:

• yo comprendo = I understand
• comprender = to understand

Spanish usually does not use the infinitive where English uses a finite verb. So:

• I understand → comprendo
• not comprender

Spanish usually uses articles more often than English, especially with nouns that are specific or already understood in context.

Here, la idea means:

• the idea

It refers to a specific idea, not just the general concept of ideas. So the definite article is needed.

Compare:

• Comprendo la idea = I understand the idea
• Tengo una idea = I have an idea

A la primera is an idiomatic expression meaning:

• on the first try
• the first time
• right away / immediately, depending on context

In this sentence, No siempre comprendo la idea a la primera means:

• I don’t always understand the idea the first time

It is a very common expression in Spanish.

You may also hear similar phrases like:

• No me sale a la primera = I don’t get it right on the first try
• Lo entendí a la primera = I understood it immediately / the first time

That la is a direct object pronoun, and it refers back to la idea.

So:

• la profesora = the teacher → subject
• la explica = explains it → la = it, referring to la idea

English says:

• the teacher explains it

Spanish does the same with the pronoun:

• la profesora la explica

Without that la, the sentence would feel incomplete, because explicar normally needs its object if you want to say what is being explained.

You tell from the word it goes with and its job in the sentence.

In la profesora la explica:

1. la profesora

   • Here la is a definite article
   • It goes before the noun profesora
   • It means the

2. la explica

   • Here la is a direct object pronoun
   • It goes before the verb explica
   • It means it, referring to la idea

So the two la words look the same, but they do different jobs.

Because the subject is la profesora, which is third person singular.

So the verb must match that subject:

• la profesora explica = the teacher explains
• las profesoras explican = the teachers explain

Here is the pattern:

• yo explico
• tú explicas
• él/ella explica
• nosotros explicamos
• vosotros explicáis
• ellos/ellas explican

Since la profesora = she / the teacher, explica is the correct form.

Because Spanish often leaves out subject pronouns when the verb form already shows who the subject is.

So instead of saying:

• pero ella la explica con calma

Spanish can simply say:

• pero la profesora la explica con calma

And even after that, if the context were clear enough, Spanish could sometimes omit the noun too:

• ...pero la explica con calma

Spanish is a pro-drop language, which means subject pronouns like yo, tú, ella, etc. are often omitted.

Con calma literally means with calm, but in natural English it means something like:

• calmly
• patiently
• without rushing
• in a relaxed way

In this sentence, it suggests that the teacher explains the idea in a calm, unhurried manner.

It is a very common expression. For example:

• Hazlo con calma = Do it calmly / Take your time
• Habla con calma = Speak calmly

Because con calma is much more natural and common in everyday Spanish.

Although calmadamente exists, it can sound more formal or less common in normal conversation. Spanish often prefers short prepositional phrases like:

• con calma
• con cuidado
• con paciencia

instead of longer adverbs.

So:

• la explica con calma sounds very natural
• la explica calmadamente is possible, but less common in ordinary speech

Yes, it is very common in Spain, and learners will hear it often.

In Spain, a la primera is a normal way to say:

• at the first attempt
• the first time
• straight away

You may also hear other expressions depending on region and style, but a la primera is standard and widely understood.

For a learner of Spanish from Spain, this is a very useful phrase to remember.

Because pero joins two clauses, and Spanish normally writes a comma before it when it connects two full ideas.

Here the two parts are:

• No siempre comprendo la idea a la primera
• pero la profesora la explica con calma

The comma helps show the contrast:

• I don’t always understand it at first, but the teacher explains it calmly.

This is similar to English, where we also often use a comma before but when joining two independent clauses.

Yes, absolutely.

You could say:

• No siempre entiendo la idea a la primera, pero la profesora la explica con calma.

That would sound natural too.

If anything, entiendo may sound a little more everyday and conversational to many speakers, while comprendo can feel slightly more formal or deliberate. But both are correct and natural.