La nouvelle stagiaire est un peu nerveuse, mais elle est très contente de travailler ici.

Because the stagiaire (intern) in this sentence is female.

• Stagiaire can be both masculine and feminine; the form doesn’t change in writing.
• The article and adjective show the gender:
  
  • la nouvelle stagiaire = the new (female) intern
  • le nouveau stagiaire = the new (male) intern
    So la and nouvelle tell you the stagiaire is a woman.

In French, some common adjectives usually go before the noun. Nouveau / nouvelle is one of them.

Typical “before-the-noun” adjectives include:

• bon / mauvais, grand / petit, beau, jeune, vieux, nouveau, joli, etc.

So you say la nouvelle stagiaire, un bon film, une petite maison, not la stagiaire nouvelle in normal, neutral style.

Because the subject, la nouvelle stagiaire, is feminine. Adjectives must agree in gender and number with the noun.

• Masculine: nerveux (un stagiaire nerveux)
• Feminine: nerveuse (une stagiaire nerveuse)

Here, stagiaire is feminine (la), so the adjective takes the feminine form nerveuse.

Same reason as with nerveuse: agreement with a feminine subject.

• Masculine: content (un stagiaire content)
• Feminine: contente (une stagiaire contente)

Since we’re talking about la stagiaire (a woman), we must use contente.

Yes. You would change everything that shows feminine gender to the masculine forms:

• La nouvelle stagiaire est un peu nerveuse, mais elle est très contente de travailler ici.
  → Le nouveau stagiaire est un peu nerveux, mais il est très content de travailler ici.

So: la → le, nouvelle → nouveau, nerveuse → nerveux, elle → il, contente → content.

Yes, that’s possible and correct in French:

• La nouvelle stagiaire est un peu nerveuse, mais très contente de travailler ici.

The verb est and the subject elle are understood from the first clause. The original version with mais elle est is slightly more explicit and a bit more careful/formal; the shorter version sounds more fluid and natural in everyday speech.

Un peu without de is used before adjectives and adverbs:

• un peu nerveuse = a little nervous
• un peu fatigué, un peu triste, un peu lentement, etc.

Un peu de is used before nouns:

• un peu de sucre, un peu de temps, un peu de chance

Here, nerveuse is an adjective, so the correct form is un peu nerveuse, not un peu de nerveuse.

Un peu softens the adjective; it makes it less strong.

• Elle est nerveuse. = She is nervous.
• Elle est un peu nerveuse. = She is a bit / a little nervous.

So un peu makes the description more moderate and less absolute.

In French:

• Très is used with adjectives and adverbs:
  
  • très contente, très grand, très fatigué, très vite
• Beaucoup is mainly used with verbs and sometimes with nouns:
  
  • Elle travaille beaucoup. (She works a lot.)
  • Beaucoup de travail.

So you say très contente, not beaucoup contente.

Many French adjectives are followed by de + infinitive to express the reason or cause of the emotion or quality.

• contente de faire quelque chose = happy to do something
• heureux de venir, triste de partir, fier de réussir, etc.

You cannot drop de here; contente travailler is incorrect. It must be contente de travailler.

No, not in standard French. After content / contente, the normal pattern is de + infinitive, not à + infinitive.

Correct:

• Elle est contente de travailler ici.

Using à travailler would sound wrong to native speakers in this context.

After adjectives like contente, French uses the infinitive to express the action linked to that feeling:

• Elle est contente de travailler ici. = She is happy to work here.

If you conjugate the verb, you change the structure and meaning:

• Elle est contente parce qu’elle travaille ici.
  Here, travaille is conjugated, and you need parce que (because). So the infinitive is required in the original structure after contente de.

Mais expresses contrast (like “but” in English):

• She is a bit nervous, but she is very happy to work here.

• Et (“and”) would just add information, without contrast:
  
  • Elle est un peu nerveuse, et elle est très contente… sounds less natural because the two ideas are opposite in tone.
• Parce que (“because”) introduces a reason, which is not the case here.

So mais is the natural choice to show two opposing aspects of her state.

Use il/elle est before an adjective describing a specific person, already identified:

• La nouvelle stagiaire est un peu nerveuse, mais elle est très contente…

C’est is used more before nouns or to introduce something more general:

• C’est une nouvelle stagiaire. = She is a new intern.
• C’est nerveux can mean “That’s (something) nervous” in a vague sense, not “She is nervous.”

Here, we’re clearly describing elle (the intern), so elle est is correct.

All three refer to place, but with different nuances:

• ici = here, close to the speaker (physically or mentally)
• là = there, close to the speaker or listener, or just “there” in a neutral way
• là-bas = over there, farther away

In travailler ici, the intern is speaking from or about the place where she actually works, so ici (“here”) is the natural choice.