Hoje eu comprei beterraba e abóbora para fazer sopa.

Yes. In Brazilian Portuguese, subject pronouns are often optional because the verb ending already shows the person.

• comprei = I bought
• so eu comprei and comprei can both mean I bought

Including eu can make the sentence:

• a little clearer
• a little more emphatic
• more natural in some contexts

So both are possible:

• Hoje eu comprei beterraba e abóbora para fazer sopa.
• Hoje comprei beterraba e abóbora para fazer sopa.

In everyday Brazilian Portuguese, people often do include eu, but omission is also common.

Comprei is the first-person singular preterite of comprar.

• comprar = to buy
• comprei = I bought

This tense is used for a completed action in the past. Here it means that the buying happened today, and the action is finished.

A quick comparison:

• compro = I buy / I am buying
• comprava = I used to buy / I was buying
• comprei = I bought
• comprarei = I will buy

Portuguese often leaves out articles when talking about ingredients, food items, or things in a general sense.

So:

• comprei beterraba e abóbora = I bought beetroot and pumpkin

This sounds natural if you are just mentioning what you bought.

You could also hear:

• comprei uma beterraba e uma abóbora
  if you mean one beet and one pumpkin
• comprei a beterraba e a abóbora
  if you mean specific ones already known in the conversation

Without articles, the sentence feels general and very natural.

Because sopa here is being used in a general sense: to make soup.

• para fazer sopa = to make soup, soup-making in general
• para fazer a sopa = to make the soup, a specific soup already known

So the sentence suggests purpose in a general way: the vegetables were bought in order to make soup.

If you were talking about a specific soup, you might say:

• para fazer a sopa de hoje
• para fazer aquela sopa

Para often means for or in order to, and when followed by an infinitive verb, it usually expresses purpose.

So:

• para fazer sopa = to make soup / in order to make soup

This is a very common structure in Portuguese:

• Comprei pão para comer no café da manhã.
  I bought bread to eat at breakfast.
• Estudo português para trabalhar no Brasil.
  I study Portuguese to work in Brazil.

So para + infinitive is a very useful pattern to learn.

Yes, you could. It changes the nuance a little.

• para fazer sopa = to make soup, generally
• para fazer uma sopa = to make a soup / some soup, a bit more specific or countable

In many everyday situations, both are possible.
But fazer sopa is very natural when you are talking about the activity in general, especially with ingredients.

Yes. Portuguese word order is fairly flexible, especially with adverbs like hoje.

These are all natural:

• Hoje eu comprei beterraba e abóbora para fazer sopa.
• Eu comprei beterraba e abóbora hoje para fazer sopa.
• Eu hoje comprei beterraba e abóbora para fazer sopa.
  possible, though a bit more marked

Starting with Hoje gives special attention to today. It sets the time right away, which is very common.

The accents in abóbora show which syllable is stressed.

• a-BÓ-bo-ra

The written accents help you pronounce it correctly. Without them, a learner might stress the wrong syllable.

In Portuguese, accent marks can:

• show stress
• sometimes also distinguish words
• sometimes indicate vowel quality

So in this word, the accents mainly help with pronunciation and stress.

A simple approximate guide:

• beterraba → beh-teh-HAH-ba
  stress on ra
• abóbora → a-BO-bo-ra
  main stress on bó
• hoje → roughly OH-zhee in many Brazilian accents

A few notes:

• the r in beterraba is usually a tapped/flapped r when between vowels
• the j in hoje sounds like the s in measure
• final e in Brazilian Portuguese often sounds like ee

These are approximations for English speakers, but they help.

Yes, both are feminine nouns:

• a beterraba
• a abóbora

It does matter when you use articles or adjectives:

• a beterraba fresca
• a abóbora grande

In the original sentence, there are no articles or adjectives, so you do not directly see the gender agreement. But if you expanded the sentence, you would need feminine forms.

Portuguese often uses singular nouns for ingredients or food substances when speaking generally.

So:

• comprei beterraba e abóbora
  can mean you bought some beetroot and some pumpkin, not necessarily just one of each

If you want to be very explicit about quantity, you can use:

• beterrabas e abóboras for plural countable items
• uma beterraba e uma abóbora for one of each
• um pouco de abóbora for some pumpkin

The singular here sounds natural because the focus is on the ingredients, not on exact count.

Yes. In Brazil, beterraba is the normal everyday word for beet or beetroot.

A native English speaker may notice that English distinguishes:

• beet
• beetroot in some varieties of English

Portuguese usually just uses beterraba.

Yes. The conjunction e normally means and, and in Brazilian Portuguese its pronunciation can vary depending on what follows.

By itself, it is often pronounced roughly like ee.
Before a word beginning with i or a similar sound, speakers may pronounce it more like i anyway.

In this sentence:

• beterraba e abóbora

it is basically the normal and, linking the two nouns. The main thing for a learner is just to recognize e as the very common word for and.