Летом мы часто едим черешню, а зимой мне больше нравится хурма.

These are time expressions used in the instrumental case.

• лето → летом
• зима → зимой

In Russian, some nouns for times and seasons can work almost like adverbs:

• утром = in the morning
• днём = in the daytime
• вечером = in the evening
• зимой = in winter
• летом = in summer

So Летом and зимой here mean in summer and in winter without needing a word like in.

Yes, but more specifically, черешня means sweet cherry.

Russian usually distinguishes:

• черешня = sweet cherry
• вишня = sour cherry / tart cherry

English often uses just cherry for both, so this is a very common vocabulary question.

Because черешню is the accusative singular form, and it is the direct object of едим.

The base form is:

• черешня = nominative

But after a verb like есть / едим when it means eat something, you use the direct object:

• Мы едим черешню

For feminine nouns ending in -я, the accusative singular often ends in -ю:

• черешня → черешню

Because Russian uses the present tense for habitual or general repeated actions, just like English does in sentences such as In summer we often eat cherries.

So едим here does not mean only right now. It means something like:

• this is what we usually do
• this happens often
• this is a general habit

The word часто helps show that habitual meaning.

Both can work, but they are not exactly the same.

• Мне нравится хурма = I like persimmon
• Я люблю хурму = I love / really like persimmon

Нравиться is often a bit softer and very common when talking about preferences.
Любить can sound stronger or more general.

So мне больше нравится хурма feels very natural for saying that persimmon is your preferred fruit in winter.

Because нравиться uses a different structure from English.

Russian treats нравиться more like to be pleasing to someone. So the person who experiences the liking goes into the dative case:

• я → мне
• ты → тебе
• он → ему
• она → ей

So:

• Мне нравится хурма

literally works like:

• Persimmon is pleasing to me

That is why мне, not я, is used.

Because with нравиться, the thing that is liked is the subject of the sentence, so it stays in the nominative case.

Compare:

• Я люблю хурму
  Here хурму is the direct object, so it is accusative.

• Мне нравится хурма
  Here хурма is the subject of нравится, so it is nominative.

A good way to remember it:

• with любить: the thing liked is an object
• with нравиться: the thing liked is the subject

Because the subject is хурма, which is singular.

With нравиться, the verb agrees with the thing that is pleasing:

• Мне нравится хурма = singular subject
• Мне нравятся яблоки = plural subject

So нравится is singular because хурма is singular.

Больше here means more, so больше нравится means likes more or prefers.

So:

• мне больше нравится хурма

means something like:

• I like persimmon more
• I prefer persimmon

Often the comparison is implied. It can mean:

• more than other fruits
• more than something else in winter
• more than what was just mentioned before

If you want to state the comparison directly, you can add чем:

• Мне больше нравится хурма, чем яблоки

А is very common when contrasting two situations, especially when both parts are true.

Here the sentence contrasts:

• летом vs зимой
• мы едим черешню vs мне больше нравится хурма

So а works well as whereas, while, or and as for the other situation.

Но usually sounds more like but in the sense of contradiction or unexpected opposition. Here there is contrast, but not really contradiction, so а is the more natural choice.

Yes. Russian word order is flexible, though some versions sound more natural than others depending on emphasis.

The original sentence starts with Летом and зимой to highlight the seasonal contrast:

• Летом мы часто едим черешню, а зимой мне больше нравится хурма.

You could also say:

• Мы летом часто едим черешню, а зимой мне больше нравится хурма.
• Зимой мне больше нравится хурма, а летом мы часто едим черешню.

The meaning stays basically the same, but the focus changes a little. The original version is very natural because it sets up the time contrast right away.

You could, but едим is the more neutral and standard choice.

• есть → едим = to eat
• кушать → кушаем = also to eat, but often feels more colloquial, childish, or extra polite depending on context

So in a normal neutral sentence like this, едим is what most learners should expect and use first.