Mi amiga es ambiciosa, pero también muy modesta cuando habla de sus éxitos.

Because amiga is the feminine form of amigo. The sentence is talking about a female friend, so Spanish uses:

• amigo = male friend
• amiga = female friend

The possessive mi stays the same for both masculine and feminine singular nouns:

• mi amigo
• mi amiga

Unlike English, the noun itself changes form to show gender.

They agree with amiga, which is feminine singular.

In Spanish, many adjectives change form to match the noun in gender and number:

• ambicioso → masculine singular
• ambiciosa → feminine singular
• modesto → masculine singular
• modesta → feminine singular

So because the subject is mi amiga, the adjectives must also be feminine singular:

• Mi amiga es ambiciosa
• Mi amiga es modesta

Spanish uses ser and estar differently, and this is a very common question for English speakers.

Here, es comes from ser, because ambiciosa and modesta describe personal characteristics or qualities. These are seen as part of who she is, not a temporary state.

• es ambiciosa = she is ambitious
• es modesta = she is modest

If you used está, it would usually suggest a temporary condition or a result of something, which does not fit naturally here.

So:

• ser = identity, characteristics, general traits
• estar = states, conditions, location

Pero means but, and también means also or too.

Together, pero también means something like:

• but also
• but she is also

It connects two qualities that may seem slightly contrasting:

• ambiciosa = ambitious
• modesta = modest

So the sentence is saying that she is ambitious, but also very modest.

Using both words makes the contrast-and-addition clearer than just pero alone.

Muy means very, and it is used to intensify an adjective or adverb.

So:

• modesta = modest
• muy modesta = very modest

This is similar to English word order:

• very modest
• muy modesta

Notice that in Spanish, muy does not change for gender or number.

Literally, it means:

• cuando = when
• habla = she speaks / talks
• de = about / of
• sus éxitos = her successes

So a more word-for-word breakdown is:

• when she talks about her successes

In natural English, that becomes:

• when she talks about her achievements
• when she speaks about her successes

Because habla is the conjugated verb form, while hablar is the infinitive.

• hablar = to speak / to talk
• habla = she speaks / he speaks / you speak (formal singular)

Here the subject is mi amiga, so Spanish uses the third person singular form:

• Mi amiga habla = My friend talks / speaks

After cuando, you normally use a conjugated verb if you are talking about an actual action:

• cuando habla = when she speaks

Because hablar de is the usual way to say to talk about something.

So:

• hablar de algo = to talk about something

Examples:

• Habla de su trabajo = She talks about her job
• Hablamos de música = We talk about music

English speakers often want to map this directly to English structure, but in Spanish the preposition de is required with this meaning.

Because éxitos is plural, and the possessive must agree with the number of the thing possessed, not with the owner.

• su éxito = his/her/your singular success
• sus éxitos = his/her/your plural successes

Even though the friend is just one person, she has multiple éxitos, so Spanish uses sus.

This is a key difference for learners: possessives in Spanish agree with the noun that follows.

The singular is éxito and the plural is éxitos. The written accent shows where the stress falls:

• ÉX-i-to
• ÉX-i-tos

Without the accent mark, Spanish pronunciation rules would suggest a different stress pattern, so the accent is necessary.

Accent marks in Spanish are not optional decoration; they are part of correct spelling and often help show pronunciation.

Mostly yes, but this version is the most natural and neutral.

Standard order here is:

• Mi amiga es ambiciosa, pero también muy modesta cuando habla de sus éxitos.

You could change some parts for emphasis, but not all changes sound equally natural. For example:

• Cuando habla de sus éxitos, mi amiga es muy modesta.
  This emphasizes the context when she talks about her successes.

But the original sentence flows well because it first gives two character traits, then adds the circumstance in which the second one is especially noticeable.

Often yes, but learners should be careful with direct one-to-one assumptions.

In this sentence, modesta clearly means modest / humble, especially about achievements. That matches English well.

However, depending on context, modesto/a can also describe something simple or not luxurious, for example:

• una casa modesta = a modest/simple house

So here the meaning is about personality, not about size, money, or style.

Because Spanish often omits subject pronouns when the verb form already makes the subject clear.

Instead of saying:

• Mi amiga es ambiciosa, pero ella también es muy modesta...

Spanish naturally says:

• Mi amiga es ambiciosa, pero también muy modesta...

Or, if the subject has already been established, it might even say:

• Es ambiciosa, pero también muy modesta...

Spanish is a pro-drop language, which means subject pronouns like yo, tú, ella are often left out unless needed for emphasis, contrast, or clarity.