Se sobrar melão, eu vou levar para minha avó junto com um pedaço de melancia.

Because after se when you are talking about a future possibility in Portuguese, Brazilian Portuguese normally uses the future subjunctive.

So:

• Se sobrar melão... = If there is melon left / If any melon is left
• not se sobra, which would sound wrong in this context

This is a very common pattern:

• Se eu tiver tempo, eu vou. = If I have time, I’ll go.
• Se ela puder, ela ajuda. = If she can, she’ll help.

The form sobrar happens to look exactly like the infinitive here, but in this sentence it is functioning as the future subjunctive.

Here sobrar means to be left over, to remain, or to be extra.

So Se sobrar melão means something like:

• If there is any melon left over
• If some melon remains

A few examples:

• Sobrou bolo. = There was cake left over.
• Se sobrar comida, eu levo. = If there’s food left over, I’ll take it.

It does not mean to know or to rise or anything like that. In this sentence it specifically refers to leftover food.

Portuguese often leaves out the article when talking about a substance or food in a general, non-specific way.

So:

• sobrar melão = if there is melon left
• um pedaço de melancia = a piece of watermelon

In English, we also often do this with mass nouns:

• There’s cake left
• I bought bread
• Do you want watermelon?

If the speaker wanted to make it more specific, an article could appear in other contexts, but here the zero article sounds natural.

Both can mean I will take, but eu vou levar is much more common in everyday Brazilian Portuguese.

• eu vou levar = I’m going to take / I will take
• levarei = I will take

The simple future levarei is correct, but it often sounds more formal, literary, or less conversational.

In normal speech, Brazilians usually prefer:

• vou fazer
• vou falar
• vou levar

rather than:

• farei
• falarei
• levarei

Yes. Portuguese often drops subject pronouns when the verb already makes the subject clear.

So both are natural:

• Se sobrar melão, eu vou levar...
• Se sobrar melão, vou levar...

Including eu can add a little emphasis, clarity, or simply reflect the speaker’s style. In Brazilian Portuguese, subject pronouns are used more often than in European Portuguese, but they are still often optional.

In Portuguese, the difference between levar and trazer is based on direction, much like take and bring in English.

• levar = to take something away from where the speaker is
• trazer = to bring something toward where the speaker is

Here, the speaker plans to take the melon to the grandmother, so levar is the natural choice.

• Vou levar para minha avó. = I’m going to take it to my grandmother.

If the speaker were talking about bringing something here, toward themselves, then trazer would be used.

Yes, both are possible, but they are used a little differently.

• levar para minha avó is very common in Brazilian Portuguese and sounds natural in everyday speech.
• levar à minha avó is more formal and uses the preposition a plus the article a = à.

So these are both understandable:

• Vou levar para minha avó.
• Vou levar à minha avó.

In everyday Brazilian Portuguese, para is usually much more common.

In Brazilian Portuguese, possessives can appear either with or without the definite article, depending on the region, style, and sentence.

So both can occur:

• minha avó
• a minha avó

In Brazil, omitting the article is very common, especially in simpler, neutral speech. Using the article is also possible in many contexts, but it can sound more regional or stylistically different.

So para minha avó is completely natural.

Junto com means together with or along with.

So:

• junto com um pedaço de melancia = together with a piece of watermelon

You could also say just com um pedaço de melancia, and the meaning would be very similar:

• Vou levar melão com um pedaço de melancia.

But junto com makes the idea of in addition / along with a little more explicit.

It emphasizes that the melon is being taken together with another item.

Because the speaker is talking about the two fruits in different ways.

• melão appears as a general quantity: some melon, melon left over
• um pedaço de melancia is a specific countable portion: one piece of watermelon

So the grammar reflects how the food is being viewed:

• melão = an uncounted amount
• um pedaço de melancia = one piece/slice/chunk

This is similar to English:

• If there’s melon left...
• ...with a piece of watermelon.

Not exactly.

• pedaço = piece, chunk, portion
• fatia = slice

Pedaço is more general. It can be used for many kinds of pieces.
Fatia suggests a sliced piece, often flatter or more regular.

With fruit, both may be possible depending on what the piece looks like, but pedaço de melancia is a very natural general choice.

Because Se sobrar melão is an introductory conditional clause.

The comma separates:

• the condition: Se sobrar melão
• the main clause: eu vou levar para minha avó...

This is similar to English punctuation:

• If there’s melon left, I’m going to take it...

In Portuguese, this comma is standard and helps make the sentence easier to read.

Yes, but the meaning would become more specific.

• Se sobrar melão = if there is melon left / if any melon is left
• Se sobrar o melão = if the melon is left / if that specific melon remains

Using o melão points to a specific melon already known in the conversation. Without the article, the sentence sounds more general and natural in this context.

It is doing both in a practical sense, but most importantly it marks the recipient/destination.

• levar para minha avó = take to my grandmother

So para shows who the item is being taken to. This is very common with verbs of movement and transfer in Brazilian Portuguese.

Examples:

• Levei flores para minha mãe. = I took flowers to my mother.
• Vou mandar isso para ele. = I’m going to send this to him.

Yes, there is some flexibility, though the original order is very natural.

Original:

• Se sobrar melão, eu vou levar para minha avó junto com um pedaço de melancia.

You might also hear:

• Se sobrar melão, eu vou levar junto com um pedaço de melancia para minha avó.

Both are understandable. The original version sounds smooth and clear because para minha avó comes right after levar, and then junto com... adds the extra item afterward.

No. Avó just means grandmother in general.

Portuguese does not have separate everyday words for maternal and paternal grandmother. If you need to specify, you would say something like:

• minha avó materna = my maternal grandmother
• minha avó paterna = my paternal grandmother

But in normal conversation, avó is enough.