Durante o recreio, uma colega escreveu no quadro com giz branco.

Yes. In European Portuguese, recreio very commonly means recess / break time at school.

So:

• durante = during
• o recreio = the recess / the school break

In this sentence, Durante o recreio means During recess or During the break.

Yes, you could.

• no recreio = at recess / during recess
• durante o recreio = during recess

Both are natural, but durante o recreio sounds a bit more explicit about the time frame. No recreio is often a little shorter and more everyday.

Because Durante o recreio is an introductory time phrase.

In English, this is similar to writing:

• During recess, a classmate wrote...

The comma helps separate that opening time expression from the main clause. It is very normal here.

Literally, colega means colleague / peer / classmate, depending on context.

In a school sentence like this, uma colega most naturally means:

• a female classmate
• or a female schoolmate / peer

So even though colega often looks like colleague in English, here classmate is probably the best natural interpretation.

Because uma is the indefinite article, meaning a / one, while a is the definite article, meaning the.

So:

• uma colega = a classmate / one classmate
  someone not specifically identified
• a colega = the classmate
  a specific classmate already known from context

In this sentence, the person is being introduced as a classmate, not the particular classmate.

No. Colega is a common-gender noun. That means the noun form stays the same, and the article tells you whether the person is male or female.

• um colega = a male classmate / colleague
• uma colega = a female classmate / colleague

So the -a ending does not automatically make it feminine.

Escreveu is the pretérito perfeito simples, which corresponds to the simple past in English in this kind of sentence.

It means the action is seen as completed:

• escreveu = wrote

So the sentence presents this as a finished event that happened during recess.

Because Portuguese often leaves out subject pronouns when they are not needed. This is very common.

Here, the subject is already clearly given:

• uma colega escreveu...

So adding ela would usually be unnecessary.

Portuguese does this much more often than English.

Because no is a contraction of:

• em + o = no

So:

• no quadro = on the board / literally in the board

After escrever, Portuguese commonly uses em with surfaces like boards, paper, walls, etc.

Examples:

• escrever no quadro = write on the board
• escrever no caderno = write in the notebook

Quadro can mean different things in different contexts, such as:

• picture
• frame
• board

In a classroom sentence like this, quadro means the board.

It does not by itself tell you whether it is a blackboard or a whiteboard. Context decides that.

If you want to specify whiteboard, you can say:

• quadro branco

So this sentence does not mean that the board was white. It only says that the chalk was white.

Because com means with, and here it shows the instrument/material used.

So:

• com giz branco = with white chalk

This tells you what she used to write.

Both are possible, but they are slightly different.

• com giz branco = with white chalk
  general, natural, focusing on the material
• com um giz branco = with a piece of white chalk
  more specific, emphasizing one piece/stick

Portuguese often leaves out the article when talking about a material or means in a general way, so com giz branco sounds very normal.

Because branco agrees with giz, and giz is a masculine singular noun.

So:

• giz branco = white chalk

Even though English learners often focus on word endings, noun gender in Portuguese is not always predictable from the ending alone. Giz is masculine, so the adjective must also be masculine singular:

• branco

It describes the chalk.

The structure is:

• com giz branco = with white chalk

If you wanted to say the board was white, you would need something like:

• no quadro branco = on the whiteboard

So in this sentence:

• quadro = board
• giz branco = white chalk

Because in Portuguese, adjectives often come after the noun.

So:

• giz branco = white chalk

This is the normal order. Sometimes adjectives can come before the noun, but that usually changes style or emphasis. Here, the standard order is the natural one.

Yes. Portuguese word order is fairly flexible.

For example, you could also say:

• Uma colega escreveu no quadro com giz branco durante o recreio.

That is still grammatical. The original version starts with Durante o recreio because it puts the time setting first.

So the original word order helps highlight when it happened.