Para desayunar, solo quiero una rebanada de pan con queso.

Para + infinitive is a very common Spanish structure meaning for doing something or in order to do something.

So para desayunar literally means for having breakfast. In natural English, that often becomes simply for breakfast.

You could also hear:

• Para el desayuno = for breakfast
• En el desayuno = at breakfast / during breakfast

But para desayunar sounds very natural when talking about what you want to eat for that meal.

Because after para, Spanish often uses an infinitive when the subject is general or understood.

Examples:

• para comer = to eat / for eating
• para cenar = for dinner / to have dinner
• para desayunar = for breakfast / to have breakfast

So here, desayunar is not acting as the main verb. It is part of the phrase para desayunar.

Because Para desayunar is an introductory phrase placed at the beginning of the sentence.

The comma helps separate that opening idea from the main statement:

• Para desayunar, solo quiero...

In short:

• Para desayunar = setting the context
• solo quiero... = the main message

In informal writing, some people might omit the comma, but using it is clear and standard.

Both are correct and both can mean only.

• solo = only
• solamente = only / just

In this sentence, solo is shorter and more natural in everyday speech:

• Solo quiero una rebanada... = I only want one slice...

Solamente would sound a little more formal or emphatic:

• Solamente quiero una rebanada...

Modern standard Spanish usually writes solo without an accent, even when it means only.

Older spelling rules sometimes used sólo to distinguish it from the adjective solo meaning alone, but the current standard is generally solo in both cases unless there is real ambiguity.

So in this sentence:

• solo quiero = I only want

That is completely normal.

Quiero means I want, which is direct and very common.

• Quiero = I want
• Me gustaría = I would like

So:

• Solo quiero una rebanada de pan con queso = direct, simple
• Solo me gustaría una rebanada de pan con queso = softer, more polite

Neither is wrong. Quiero is just more straightforward.

Because pan is usually treated as an uncountable noun, like bread in English.

If you want to talk about one piece, Spanish often uses a unit word:

• una rebanada de pan = a slice of bread
• un trozo de pan = a piece of bread

So una rebanada de pan is the natural way to say a slice of bread.

Because rebanada is a feminine noun.

That means it takes:

• una rebanada
• not un rebanada

A good clue is the ending -a, which often marks feminine nouns, though not always.

Because Spanish uses noun + de + noun for this kind of partitive expression.

So:

• una rebanada de pan = a slice of bread
• un vaso de agua = a glass of water
• una taza de café = a cup of coffee

The de connects the portion to the whole thing.

Because con queso means with cheese — in other words, bread that has cheese on it or served with it.

• pan con queso = bread with cheese
• pan de queso would usually mean a kind of cheese bread, where the cheese is part of the bread itself

So if you mean a slice of bread topped or accompanied by cheese, con queso is the correct choice.

Yes. Spanish word order is flexible, though some positions sound more natural than others.

The original:

• Para desayunar, solo quiero una rebanada de pan con queso.

This clearly means:

• For breakfast, I only want a slice of bread with cheese.

You could also say:

• Para desayunar, quiero solo una rebanada de pan con queso.

That is also understandable, but the original version sounds more natural and flows better in everyday Spanish.

No. There are other possibilities, but rebanada is a very good general choice here.

For example:

• rebanada = slice
• trozo = piece
• tostada = toast / a slice of toasted bread

So if the bread is toasted, you might also hear:

• solo quiero una tostada con queso

But if you specifically mean a slice of bread, una rebanada de pan is perfectly natural.