Мы заморозили ягоды летом, чтобы зимой пить компот.

Заморозили is the perfective past form, so it presents the action as completed: we froze the berries successfully, as a finished act.

• замораживать / заморозить = to freeze
• морозили would usually suggest an ongoing, repeated, or process-focused action: we were freezing, we used to freeze, or we froze them for some time

In this sentence, the speaker means the berries were put into the freezer as a completed preparation for winter, so заморозили is the natural choice.

Ягоды is the accusative plural here because it is the direct object of заморозили.

The dictionary form is ягода = berry.

Plural:

• Nominative: ягоды
• Accusative: ягоды

Because ягоды refers to inanimate things, the accusative plural looks the same as the nominative plural. So:

• ягоды лежат на столе = the berries are lying on the table
• мы заморозили ягоды = we froze the berries

Same form, different job in the sentence.

In Russian, words for seasons are often put in the instrumental case to mean in the summer, in the winter, etc.

So:

• лето → летом = in summer
• зима → зимой = in winter

This is a very common time expression pattern:

• весной = in spring
• летом = in summer
• осенью = in autumn
• зимой = in winter

English uses a preposition (in summer), but Russian often does not here.

Чтобы means so that, in order to, or for the purpose of.

It introduces the purpose of the first action:

• Мы заморозили ягоды летом = We froze berries in the summer
• чтобы зимой пить компот = so that we could drink compote in winter

So the whole sentence expresses doing one thing for a later purpose.

After чтобы, Russian often uses the infinitive when the subject is the same as in the main clause.

Here:

• Мы заморозили...
• and the same we are the ones who will drink

So чтобы зимой пить компот is a natural infinitive construction: so as to drink compote in winter.

Why пить and not выпить?

• пить is imperfective, focusing on the activity/process of drinking
• выпить is perfective, often meaning to drink up / finish drinking / drink once as a completed act

Since the idea is general winter enjoyment, not one single completed drink, пить works better.

Компот is a traditional drink made by boiling fruit or berries in water, usually with sugar. It is very common in Russian-speaking cultures.

It is often translated as fruit compote or simply left as kompot/compote, depending on the context. In this sentence, the idea is that the berries were frozen in summer so they could later be used to make this drink in winter.

So пить компот means to drink compote.

Russian often does not need a separate word like can in this type of purpose sentence.

English might say:

• so that we could drink compote in winter
• in order to drink compote in winter

Russian simply says:

• чтобы зимой пить компот

The idea of purpose is already built into чтобы, so adding something like мочь is often unnecessary unless you specifically want to emphasize ability.

No, Russian word order is fairly flexible, though the original order is very natural.

Original:

• Мы заморозили ягоды летом, чтобы зимой пить компот.

This flows well because it goes:

1. subject
2. completed action
3. object
4. time
5. purpose
6. later time
7. final action

You could move things around for emphasis, for example:

• Летом мы заморозили ягоды, чтобы зимой пить компот.
• Мы летом заморозили ягоды, чтобы зимой пить компот.

These are all understandable, but the original sentence sounds smooth and neutral.

In this sentence, the default understanding is that the subject is the same as in the main clause: we.

So:

• Мы заморозили ягоды летом, чтобы зимой пить компот. naturally means:
• We froze berries in the summer so that we could drink compote in winter.

If Russian wanted to make a different subject explicit, it would usually say so:

• ..., чтобы дети зимой пили компот = so that the children would drink compote in winter

So with just the infinitive пить, the understood subject is normally the same as мы.

Because Russian normally does not say в лето or в зиму to mean in summer or in winter.

Instead, it uses these adverbial instrumental forms:

• летом
• зимой

This is just the standard idiomatic pattern. A learner should treat these almost like set expressions:

• летом = in summer
• зимой = in winter

It can mean either, depending on context.

In this sentence, ягоды could be understood as:

• the berries we had
• or just berries in a general sense

Russian often omits articles because it has no a / an / the. So the exact nuance comes from context rather than from a separate word.

Here, English could translate it as:

• We froze the berries in summer... or
• We froze berries in summer...

Both are possible depending on the situation.

Yes, it sounds natural.

It expresses a very common real-life idea:

• prepare food in one season
• use it later for another season

The structure is straightforward and idiomatic:

• Мы заморозили ягоды летом = completed preparation
• чтобы зимой пить компот = purpose

A native speaker would find this sentence normal and clear.