На рынке я купил фасоль и чечевицу, потому что собираюсь готовить супы на всю неделю.

In Russian, на рынке is the normal way to say at the market or in the marketplace.

A useful pattern is:

• на рынке = at the market
• на вокзале = at the station
• на почте = at the post office

Even though English often uses in, Russian idiomatically uses на with some public places or open-area locations.

So На рынке я купил... means At the market, I bought...

Yes, both are possible.

Russian word order is much more flexible than English word order. The version in your sentence puts extra focus on На рынке:

• На рынке я купил фасоль и чечевицу... = At the market, I bought beans and lentils...
• Я купил фасоль и чечевицу на рынке... = I bought beans and lentils at the market...

The meaning is basically the same, but the emphasis changes a little.

In this sentence, starting with На рынке helps set the scene first.

This is a question of aspect.

• купить / купил = perfective, focusing on a completed result
• покупать / покупал = imperfective, focusing on the process, repetition, or background action

Here, the speaker is talking about one completed purchase: they bought the items. So купил is the natural choice.

Compare:

• Я купил фасоль. = I bought beans. The purchase is completed.
• Я покупал фасоль. = I was buying / used to buy beans / bought beans at some point, with more focus on the process or context.

Yes. In the past tense, Russian verbs show gender in the singular.

• купил = masculine speaker
• купила = feminine speaker
• купило = neuter
• купили = plural

So this sentence suggests that the speaker is male, unless this is just being used as a dictionary-style example.

If the speaker were female, it would be:

На рынке я купила фасоль и чечевицу...

Because both nouns are in the accusative case as direct objects of купил, but they belong to different declension patterns.

• фасоль is a feminine noun ending in a soft sign (-ь)
• чечевица is a feminine noun ending in -а

In the accusative singular:

• фасоль stays фасоль
• чечевица becomes чечевицу

So:

• nominative: фасоль, чечевица
• accusative: фасоль, чечевицу

This is normal Russian case behavior.

Russian often uses the singular for foods and ingredients when talking about them as substances or grocery items.

So:

• фасоль = beans / bean as a food item
• чечевица = lentils / lentil as a food item

This is similar to how English says I bought rice or I bought pasta, even though there are many grains or pieces.

Russian can use plural forms in some contexts, but for shopping or ingredients, the singular is very common and natural here.

Собираться + infinitive means to intend to, to be planning to, or to be about to do something.

So:

• собираюсь готовить = I’m planning to cook / I intend to cook

This adds the idea of intention or plan.

By contrast:

• буду готовить = I will be cooking

That is a more neutral future statement. It says the action will happen, but it does not highlight the speaker’s plan in the same way.

Here, собираюсь готовить fits well because the speaker is explaining why they bought the ingredients.

Yes, суп is possible, but it would mean something slightly different.

• готовить супы suggests making soups in general, possibly different kinds, or making soup multiple times
• готовить суп suggests making soup as one dish or treating it as a general activity in a more singular way

In this sentence, супы на всю неделю sounds natural because the speaker is preparing soup meals for the whole week, perhaps several batches or several kinds.

So the plural helps express repeated or varied meals over the week.

Here на всю неделю means for the whole week or to last the whole week.

The structure на + accusative is often used for something prepared, planned, or intended for a certain period:

• еды на два дня = food for two days
• денег на месяц = money for a month
• супы на всю неделю = soups for the whole week

So the idea is not just that the cooking happens during the week, but that the soups are meant to cover that whole period.

This is a very useful distinction.

• всю неделю = all week long, throughout the week
• на всю неделю = for the whole week, enough to last the week

Compare:

• Я готовил всю неделю. = I was cooking all week.
• Я приготовил еды на всю неделю. = I prepared food for the whole week.

In your sentence, на всю неделю means the soups are intended to last for the week, not that the person will literally be cooking the entire week.

Because потому что introduces a subordinate clause: because I’m planning to cook soups for the whole week.

Russian normally separates this kind of clause with a comma:

• Я купил фасоль и чечевицу, потому что собираюсь готовить супы...

This is standard punctuation.

English does not always require a comma before because, but Russian generally does in this kind of sentence.

It is accusative singular feminine.

The noun неделя is feminine, and after на in this meaning, Russian uses the accusative case.

So:

• nominative: вся неделя
• accusative: всю неделю

Both words change:

• вся → всю
• неделя → неделю

That is why you get:

на всю неделю = for the whole week