Depois de entrar na universidade, ela passou a estudar de manhã e a trabalhar à tarde.

No. In this sentence, passou a + infinitive means began to / came to / started to.

So:

• ela passou a estudar = she started studying / she began to study
• ela passou a trabalhar = she started working

This is a very common Portuguese structure:

• passar a fazer = to start doing
• passar a entender = to come to understand
• passar a morar = to start living

It does not mean she literally passed something.

Because after depois de in Portuguese, you normally use either:

• a noun, or
• an infinitive

So:

• depois da aula = after class
• depois de entrar na universidade = after entering university / after getting into university

The de is required here.
A good pattern to remember is:

• antes de + infinitive = before doing
• depois de + infinitive = after doing

Examples:

• Antes de sair, feche a porta. = Before leaving, close the door.
• Depois de chegar, me liga. = After arriving, call me.

Na = em + a.

The verb entrar often uses em when talking about entering a place:

• entrar em casa
• entrar no carro
• entrar na universidade

So:

• na universidade = into the university / at university, depending on context

Here, entrar na universidade usually means to get into university / start university / enter university as a student.

This is different from motion with ir a:

• vou à universidade = I go to the university
• entrei na universidade = I entered/got into the university

In this context, it normally means getting into university / starting university, not just walking into a university building.

The clue is the rest of the sentence:

• Depois de entrar na universidade, ela passou a estudar de manhã e a trabalhar à tarde.

This sounds like a change in her life routine after she became a university student.

So although entrar na universidade can literally mean enter the university, in everyday use it often means to enter higher education / get admitted / start attending university.

Because the structure is passar a + infinitive.

So we get:

• passou a estudar
• passou a trabalhar

The second a is repeated because the second verb also belongs to the same pattern. This makes the sentence balanced and clear.

You may hear people say:

• ela passou a estudar de manhã e trabalhar à tarde

That can happen in speech, but the more careful and standard version is the one in your sentence:

• ela passou a estudar de manhã e a trabalhar à tarde

Yes, that version is possible and common, especially in less formal writing or speech.

But the sentence with both a's is more explicit and often sounds more polished:

• passou a estudar ... e a trabalhar ...

It mirrors the structure neatly:

• a estudar
• a trabalhar

So both are understandable, but the original version is especially nice stylistically.

This is one of those time expressions you mostly learn as fixed phrases:

• de manhã = in the morning
• à tarde = in the afternoon
• à noite = at night / in the evening

So Portuguese does not use the same preposition for all three.

Common set:

• de manhã
• à tarde
• à noite

You should memorize them as chunks.

Examples:

• Eu estudo de manhã.
• Ela trabalha à tarde.
• Eles saem à noite.

Because à is the contraction of:

• a (preposition) + a (article)

So:

• a + a tarde = à tarde

This is called crase in Portuguese.

The accent mark here is not a stress mark like in some other cases; it shows the contraction.

But de manhã does not involve that contraction:

• de + manhã = de manhã

So there is no crase there.

Also note that manhã has its own accent on ã, but that is part of the word itself, not the same thing as à.

Crase is the written fusion of:

• the preposition a
• with the feminine singular article a

Written together, they become à.

In time expressions, this often happens with feminine words:

• à tarde
• à noite
• às vezes

But not every expression with a has crase, and not every time expression uses it. That is why de manhã is different.

For this sentence, the safest thing is simply to remember:

• de manhã
• à tarde
• à noite

In normal Portuguese, you generally use the definite article with places like this:

• na universidade
• na escola
• no trabalho
• no hospital

So entrar na universidade sounds natural.
Em universidade by itself would sound incomplete or unnatural in this context.

Portuguese uses articles more often than English does, so this is something English speakers need to get used to.

Yes. Portuguese often allows subject pronouns to be omitted because the verb form already shows the person.

So both are possible:

• Ela passou a estudar de manhã e a trabalhar à tarde.
• Passou a estudar de manhã e a trabalhar à tarde.

The pronoun ela may be included for:

• clarity
• emphasis
• contrast
• style

Since passou could refer to he/she/you (formal) depending on context, keeping ela makes the subject completely clear.

Passou is the pretérito perfeito of passar.

Here it refers to a completed change in the past:

• ela passou a estudar... = at some point, she began to study...

This tense often marks an event or transition:

• Começou a chover. = It started raining.
• Ela passou a trabalhar em casa. = She started working from home.

So passou marks the moment when her routine changed.

You often can use começou a here:

• Depois de entrar na universidade, ela começou a estudar de manhã e a trabalhar à tarde.

That would mean After entering university, she started studying in the morning and working in the afternoon.

But passou a often emphasizes a new habit or new state that began from then on, not just the starting moment.

Very roughly:

• começou a = started to
• passou a = came to / began to do as a new pattern

So in this sentence, passou a fits very well because it describes a change in her regular schedule.

Yes. In most everyday contexts, de manhã covers the general idea of in the morning.

Examples:

• Eu trabalho de manhã. = I work in the morning.
• Ela estuda de manhã. = She studies in the morning.

It usually refers to the part of the day when the activity happens, not necessarily every minute of the morning.

Not exactly. Universidade is most directly university.

Depending on context, an English translation might say college, especially in American English, because English speakers often say go to college where Portuguese says entrar na universidade or fazer faculdade.

But word-for-word:

• universidade = university

So the best interpretation depends on context and dialect of English.

Yes, absolutely.

Although depois de entrar na universidade is literally after entering the university, a more natural English translation in context is often:

• After starting university...
• After getting into university...
• After beginning college...

That is because the Portuguese expression often refers to becoming a university student, not physically entering a building.

Yes. Depois de entrar na universidade sets the time/background for the main action.

Structure:

• Depois de entrar na universidade = after entering university
• ela passou a estudar de manhã e a trabalhar à tarde = she started studying in the morning and working in the afternoon

So the sentence tells you when her new routine began.

This kind of opening phrase is very common in Portuguese:

• Depois de terminar o curso, ele viajou.
• Antes de sair de casa, tomei café.

In natural Brazilian speech, it would usually flow smoothly, with the opening phrase setting the scene and a slight pause after it:

• Depois de entrar na universidade, ela passou a estudar de manhã e a trabalhar à tarde.

A learner should especially notice these chunks:

• depois de entrar
• na universidade
• passou a estudar
• de manhã
• à tarde

If you learn those as units, the sentence becomes much easier to understand and produce.