Muchos estudiantes prefieren una jornada parcial porque todavía estudian en la universidad.

Because the subject is plural.

• Muchos estudiantes = they (third person plural).
• The verb preferir in the present tense:
  • él / ella / usted prefiere (singular)
  • ellos / ellas / ustedes prefieren (plural)

So we need prefieren to agree with Muchos estudiantes.
If the subject were singular, for example Un estudiante prefiere…, then prefiere would be correct.

In Spain, jornada usually refers to the working day / working hours / work schedule, not the job itself.

• jornada completa = full‑time working hours
• jornada parcial = part‑time working hours

So una jornada parcial focuses on how many hours you work (or how your schedule is organized), not on the type of job or profession.
For job in general, you’d more often use trabajo, puesto, or empleo.

Because jornada is a feminine noun in Spanish.

• Feminine singular article: una
• Masculine singular article: un

So you say:

• una jornada (feminine)
• un trabajo (masculine)

The adjective parcial doesn’t change here because it ends in -l, which has the same form for masculine and feminine in the singular:

• una jornada parcial
• un trabajo parcial

In standard Spanish, you normally include the article here: prefieren una jornada parcial.

• Saying prefieren jornada parcial (without una) sounds incomplete or non‑native in this context.
• You can, however, remove the article if jornada parcial is used more like a label in e.g. forms or headlines, but in a normal sentence the article is expected.

You could also express the idea in a more natural alternative way:

• Muchos estudiantes prefieren trabajar a tiempo parcial.
  (Many students prefer to work part‑time.)

Porque (one word, no accent on que) means because and introduces a reason:

• No voy porque estoy cansado. = I’m not going because I’m tired.

Por qué (two words, with an accent on qué) means why and is used in questions:

• ¿Por qué no vienes? = Why aren’t you coming?

In your sentence, we are giving a reason (not asking a question), so we use porque:

• …prefieren una jornada parcial porque todavía estudian en la universidad.
  = They prefer a part‑time schedule because they still study at university.

The other forms:

• porqué (one word, with accent) is a noun meaning the reason.
• por que (two words, no accent) appears in some more advanced constructions, but not here.

Both positions are grammatically correct:

• …porque todavía estudian en la universidad.
• …porque estudian todavía en la universidad.

However, the most common and neutral position for todavía in this type of sentence is before the verb.

Rough nuance:

• todavía estudian → slightly more natural and typical.
• estudian todavía → also correct; sometimes feels a bit more emphatic or stylistic, depending on context.

In everyday speech, most speakers would choose todavía estudian here.

In most cases, todavía and aún both mean still / yet and can be exchanged without changing the meaning much.

You could say:

• …porque todavía estudian en la universidad.
• …porque aún estudian en la universidad.

Both are correct.

Small nuances:

• In Spain, todavía is generally more frequent in spoken language.
• aún can sound a bit more formal or literary in some contexts, but it is also used in everyday speech.
• In some negative contexts, one may be preferred locally (e.g. todavía no, aún no), but both are widely understood and accepted.

Spanish uses the simple present much more than English to talk about actions that are ongoing at the present time.

Both are possible:

• todavía estudian en la universidad
• todavía están estudiando en la universidad

Differences:

• estudian = neutral, standard way to say they are currently students / currently study there.
• están estudiando = emphasizes the ongoing activity right now, or a temporary process.

In this sentence, we’re describing their general situation (they are still university students), so the simple present estudian is more natural.

Because here we mean at university / in university, i.e. the place or institution where they study, not movement towards it.

• en la universidad = at / in the university (location)
• a la universidad = to the university (direction, movement)

Examples:

• Estudian en la universidad. = They study at university.
• Van a la universidad en autobús. = They go to the university by bus.

So en la universidad is correct in your sentence.

In Spanish, you usually need the article with universidad when you refer to it like this:

• Estudia en la universidad. = He/She studies at university.

There are a few set expressions where the article is dropped with other nouns (e.g. ir a clase, estar en casa), but universidad normally takes the article.

So:

• ✅ en la universidad
• ❌ en universidad (sounds incorrect in standard Spanish)

Yes, that is correct, and there is a small nuance:

• Muchos estudiantes… = many students (in general; we’re just talking about a large number, without specifying a particular group)
• Muchos de los estudiantes… = many of the students (a specific set or group of students that we both know or have already mentioned)

So if you are talking about students at one particular company or in one specific class you’ve already mentioned, Muchos de los estudiantes… may fit better.
If you are speaking more generally about students as a group, Muchos estudiantes… is more natural.

Todavía is stressed on the syllable -ví-: to‑da‑VÍ‑a.

It has an accent mark because:

• It is a four‑syllable word ending in a vowel.
• Words ending in a vowel are normally stressed on the second‑to‑last syllable.
• Here the stress falls on the third‑to‑last syllable (ví), which is irregular.
• So Spanish spelling rules require a written accent: todavía.

Without the accent (todavia), a learner might incorrectly guess the stress as to‑DA‑via, which would be wrong.