Mi compañera resume muy bien las ideas principales, pero yo todavía prefiero escribir un resumen más largo para memorizar mejor el vocabulario.

Because compañera is a feminine noun meaning female classmate / colleague / partner, depending on context.

• compañero = a male classmate/colleague
• compañera = a female classmate/colleague

Here, mi compañera means my female classmate/colleague. The possessive mi does not change for masculine or feminine singular nouns, so it is mi compañero and mi compañera.

These are two different words:

• resume = the verb resumir conjugated for she or he
• resumen = a noun meaning summary

So in the sentence:

• Mi compañera resume muy bien... = My classmate summarizes ... very well
• escribir un resumen = to write a summary

This pair is very useful to remember:

• resumir = to summarize
• resumen = summary

Because it is the present tense of resumir for él / ella / usted.

The present tense goes like this:

• yo resumo
• tú resumes
• él/ella/usted resume
• nosotros resumimos
• vosotros resumís
• ellos/ellas/ustedes resumen

Since the subject is mi compañera, the correct form is resume.

Bien means well, and muy means very.

So:

• resume bien = she summarizes well
• resume muy bien = she summarizes very well

This is the normal way to intensify an adverb in Spanish:

• muy + adverb/adjective

Here bien is an adverb, so muy bien means very well.

In Spanish, adjectives usually come after the noun, so:

• ideas principales = main ideas

That is the most neutral and common order. You can sometimes put adjectives before the noun, but that often changes the tone or emphasis. For everyday Spanish, las ideas principales is the standard phrasing.

Yes, Spanish often drops subject pronouns because the verb ending already shows the subject:

• prefiero already means I prefer

So yo is not necessary for grammar, but it is often added for emphasis or contrast. Here the sentence contrasts two people:

• Mi compañera does one thing
• pero yo do something different

So yo helps emphasize I, on the other hand.

Here todavía means still.

So:

• yo todavía prefiero... = I still prefer...

It suggests that, even now, this is still the speaker’s preference.

In many contexts, todavía and aún can both mean still:

• todavía prefiero
• aún prefiero

Both are correct, though todavía is very common in everyday speech.

Because preferir is a stem-changing verb. In the present tense, the e in the stem changes to ie in most forms.

Present tense of preferir:

• yo prefiero
• tú prefieres
• él/ella/usted prefiere
• nosotros preferimos
• vosotros preferís
• ellos/ellas/ustedes prefieren

So yo prefero is incorrect. The correct form is yo prefiero.

Because after preferir, Spanish usually uses an infinitive to say what someone prefers to do:

• prefiero escribir = I prefer to write
• prefiero estudiar = I prefer to study
• prefiero leer = I prefer to read

This is similar to English I prefer to write, although Spanish often does not need a separate word for to before the second verb.

It means a longer summary.

Breakdown:

• un resumen = a summary
• más largo = longer

Spanish commonly forms comparatives with:

• más + adjective

So:

• largo = long
• más largo = longer

Here resumen is masculine singular, so the adjective is also masculine singular:

• un resumen más largo

Because largo refers to length, while mayor usually means older, greater, or bigger depending on context.

For a text, summary, document, speech, etc., Spanish normally uses largo to mean long:

• un resumen largo = a long summary
• un texto largo = a long text

So más largo is the natural choice for longer here.

Para often means in order to or so that, and it is commonly followed by an infinitive when the subject stays the same.

So:

• para memorizar mejor el vocabulario = in order to memorize the vocabulary better

This structure is very common:

• estudio para aprender
• leo para practicar
• escribo para recordar

Because mejor is modifying the verb memorizar, so it works as an adverb meaning better.

• memorizar mejor = to memorize better

In Spanish, adverbs often come after the verb or infinitive they modify. So this order sounds natural.

Because vocabulario is often used as an uncountable or collective noun, like vocabulary in English.

So:

• memorizar el vocabulario = memorize the vocabulary

It refers to vocabulary in general, not just one word. Spanish often uses the singular for this kind of idea.

You could also talk about palabras if you mean individual words:

• memorizar palabras nuevas = memorize new words

Yes, basically. Memorizar means to memorize.

In language-learning contexts, it can refer to learning words or expressions so you remember them well. In everyday Spanish, people may also say things like:

• aprender de memoria = to learn by heart / memorize
• recordar = to remember

But in this sentence, memorizar is perfectly natural.

Because pero means but, and it introduces a contrast.

The contrast is:

• My classmate summarizes the main ideas very well
• but I still prefer to write a longer summary

So pero links two different habits or preferences.

Yes. Compañera can mean different things depending on the situation:

• classmate
• coworker / colleague
• companion
• sometimes partner

In a learning sentence like this, classmate is often the most likely meaning, especially because the sentence talks about summaries, main ideas, and vocabulary. But the exact translation depends on context.