Na minha folha, eu sempre deixo uma margem grande para notas e comentários.

Na is the contraction of em + a.

• em = in/on
• a = the
• na = in/on the

So na minha folha literally works like on my sheet/page.

In Portuguese, a possessive like minha often appears with an article:

• na minha folha
• no meu caderno
• na minha mesa

You may also hear em minha folha, but na minha folha sounds more natural and common in everyday Brazilian Portuguese.

Folha usually means sheet or leaf, depending on context.

In this sentence, folha most likely means:

• a sheet of paper
• a page
• the physical writing surface you are using

That is a little different from some related words:

• folha = sheet/page/leaf
• papel = paper as a material
• página = page, especially in a book, notebook, or website

So na minha folha suggests on my sheet/page, especially a piece of paper you are writing on.

The comma separates the introductory phrase Na minha folha from the main clause.

• Na minha folha, eu sempre deixo...

This is similar to English when you start with something like:

• On my page, I always leave...

The comma is natural and clear, but in informal writing you may sometimes see it omitted. With the sentence written this way, the comma helps readability.

Yes. In Portuguese, subject pronouns are often omitted because the verb ending already shows the subject.

So both are possible:

• Eu sempre deixo uma margem grande...
• Sempre deixo uma margem grande...

Both mean the same thing here.

Including eu can do a few things:

• add emphasis
• make the sentence clearer
• sound a bit more explicit or contrastive

In this sentence, eu is not required, but it is completely natural.

Here deixo comes from deixar, and it means something like:

• I leave
• I keep
• I set aside

So eu sempre deixo uma margem grande means I always leave a big margin.

But deixar is a very flexible verb in Portuguese. It can also mean:

• to let / allow
  
  • Deixa eu ver. = Let me see.
• to leave something somewhere
  
  • Deixei o livro na mesa. = I left the book on the table.
• to stop / quit / abandon in some contexts
  
  • Deixei de fumar. = I quit smoking.

So the exact meaning depends on context.

Yes, sempre can move around, but some positions sound more natural than others.

In this sentence:

• eu sempre deixo uma margem grande...

This is the most neutral and natural order.

You can also hear:

• sempre deixo uma margem grande...
• eu deixo sempre uma margem grande...
• eu deixo uma margem grande sempre...

But the last two can sound less natural or more marked, depending on rhythm and context.

A good default pattern is:

• subject + sempre + verb

So eu sempre deixo is an excellent standard model.

Both are possible, but they do not feel exactly the same.

• uma margem grande = a margin that is physically large/wide
• uma grande margem = can sound a bit more literary or emphatic

In Portuguese, adjective position can affect nuance:

• after the noun often gives a more literal, descriptive meaning
• before the noun can sound more subjective, emphatic, or stylistically marked

So in an everyday sentence about page layout, uma margem grande is the most natural choice.

Because margem is a feminine noun in Portuguese:

• a margem
• uma margem
• margem grande

That is why the article is uma, not um.

The adjective grande does not change form here, because grande has the same singular form for masculine and feminine:

• um livro grande
• uma margem grande

Because the sentence is speaking about notes and comments in a general sense, not specific ones.

• para notas e comentários = for notes and comments

This is similar to English, where you also often omit the article in a general-purpose phrase.

If you added articles, the meaning would become more specific:

• para as notas e os comentários = for the notes and the comments

That sounds like you are referring to particular notes/comments already known in the conversation.

So without articles, it sounds more general and natural here.

Here para means for, expressing purpose:

• uma margem grande para notas e comentários
• a big margin for notes and comments

Yes, in spoken Brazilian Portuguese, pra is extremely common as a reduced form of para:

• ...pra notas e comentários

That sounds natural in conversation.

However:

• para is better for neutral or formal writing
• pra is more informal and more typical of speech or casual writing

So the sentence as given uses the more standard written form.

Yes, but the nuance changes.

• Na minha folha = on my sheet of paper / on my page
• Na minha página = on my page, often more clearly a page in a notebook, book, or even a website depending on context
• No meu papel = on my paper, but this is less natural if you mean the actual page layout

If you are talking about writing by hand on a sheet, folha is a very good choice.
If you are talking about a page in a notebook or book, página may fit better.

Deixo is the first-person singular present indicative of deixar.

Conjugation in the present:

• eu deixo = I leave
• você deixa = you leave
• ele/ela deixa = he/she leaves
• nós deixamos = we leave
• vocês deixam = you all leave
• eles/elas deixam = they leave

In this sentence, the present tense expresses a habit:

• eu sempre deixo... = I always leave...

So it is not necessarily happening right now; it is something the speaker regularly does.

A careful pronunciation would be roughly:

• Na minha folha, eu sempre deixo uma margem grande para notas e comentários.

Some helpful pronunciation notes:

• minha often sounds close to mee-nya
• folha sounds roughly like FOHL-ya
• deixo sounds like DAY-shoo in most of Brazil
• margem ends with a nasal sound: MAR-zhen / MAR-jeyn depending on accent
• comentários has stress on tá: co-men-TA-ree-os

In natural Brazilian speech, some words may connect smoothly, so the whole sentence can sound more fluid than the individual dictionary forms.