Моя подруга сказала, что приедет сюда ещё раз, лишь бы снова увидеть лошадей и покормить козу.

Because подруга is a feminine noun, so the possessive pronoun has to agree with it in gender, number, and case.

• мой = my, masculine
• моя = my, feminine
• моё = my, neuter
• мои = my, plural

So:

• мой друг = my male friend
• моя подруга = my female friend

Here подруга is feminine singular nominative, so моя is the correct form.

Usually it means female friend.

That is an important point for English speakers, because English girlfriend can mean either:

• a female friend, or
• a romantic partner

In Russian, подруга normally just means a female friend. If the meaning is romantic partner, Russian would usually make that clearer through context or use a different expression.

So in this sentence, моя подруга is most naturally understood as my female friend.

Because the subject is feminine: моя подруга.

In the past tense, Russian verbs agree with gender and number:

• сказал = he said
• сказала = she said
• сказало = it said
• сказали = they said

Since подруга is feminine, the verb has to be сказала.

Russian often leaves out subject pronouns when the subject is already clear from context.

Here, after Моя подруга сказала, it is obvious that the person who приедет is the same female friend. So Russian does not need она.

A fuller version would be possible:

• Моя подруга сказала, что она приедет сюда ещё раз...

But that sounds a bit more explicit than necessary. The version without она is very natural.

Russian does not do tense backshifting in the same way English often does.

English:

• She said that she would come

Russian:

• Она сказала, что приедет

Russian keeps the future form if the event is still future relative to the moment of speaking in the reported statement.

Also, приедет is the future form of the perfective verb приехать. Perfective verbs form the future with a simple form, not with будет:

• приехать → приедет = will come / will arrive

So сказала, что приедет is completely normal Russian.

Because приехать is a perfective verb, and perfective verbs in Russian have a simple future.

• приехать = to come/arrive once, as a completed event
• приедет = she will come / will arrive

Russian has two common future patterns:

1. Imperfective future: будет + infinitive

   • будет приезжать = she will be coming / will come repeatedly

2. Perfective future: one simple form

   • приедет = she will come (once, successfully arrive)

Here the idea is a single completed trip, so приедет is the right choice.

Because сюда means to here, while здесь means here.

This matters because приедет is a verb of motion. With motion toward a place, Russian uses сюда:

• приедет сюда = will come here
• она здесь = she is here

Compare:

• Я иду сюда = I am coming here
• Я здесь = I am here

So сюда is correct because the sentence is about movement toward this place.

They are close, but not identical.

• ещё раз = one more time, another time
• снова = again, anew

In this sentence:

• приедет сюда ещё раз = she will come here one more time
• снова увидеть лошадей = to see the horses again

So ещё раз emphasizes an additional visit, while снова emphasizes repeating the experience of seeing the horses.

You often can translate both as again, but the Russian wording shows a slight difference in focus.

Here лишь бы means something like:

• if only
• so long as
• just so that
• just to, as long as it means...

It expresses a strong motivation or minimal condition. The idea is that she is willing to come again for that purpose alone.

So the phrase suggests something like:

• she would come here again if only she could see the horses again and feed the goat
• she would come again just to do those things

This is a very expressive phrase in Russian. It often shows that the speaker considers the following goal important enough by itself.

Because they depend on the idea introduced by лишь бы and express the purpose/desired result of coming.

After лишь бы, Russian often uses a clause, but in sentences like this it can also be followed by infinitives in a shortened, natural structure. Here the infinitives mean what she wants to do:

• увидеть = to see
• покормить = to feed

So:

• лишь бы снова увидеть лошадей и покормить козу
  = roughly if only to see the horses again and feed the goat

The infinitives are functioning a bit like English to see / to feed after just to.

Because the sentence refers to single, completed actions.

• увидеть = to catch sight of, to see once, successfully see
• видеть = to see, be seeing
• покормить = to feed once / give food
• кормить = to feed in general, be feeding, feed regularly

Here the meaning is not general or ongoing. It is about specific acts:

• see the horses again
• feed the goat

So perfective verbs fit naturally because they present those actions as completed goals.

Because лошадей is the accusative plural form of an animate noun.

The verb увидеть takes a direct object, so horses must be in the accusative case. In Russian, for animate plural nouns, the accusative looks like the genitive plural.

• nominative plural: лошади
• genitive plural: лошадей
• accusative plural (animate): лошадей

So:

• вижу лошадей = I see horses
• увидеть лошадей = to see the horses / horses

This is a very common Russian pattern:

• Я вижу студентов
• Она любит кошек
• Мы встретили друзей

All of those use accusative forms that match the genitive because the nouns are animate.

Because коза is a feminine singular noun, and as the direct object of покормить, it goes into the accusative singular.

For many feminine nouns ending in -а, the accusative singular changes to -у:

• коза → козу
• машина → машину
• девушка → девушку

So:

• покормить козу = to feed the goat

This is just the regular accusative singular ending for that noun type.

Because Russian simply reflects whatever the speaker means: apparently there are multiple horses and one goat.

There is no rule saying coordinated objects have to match in number. So this is perfectly natural:

• увидеть лошадей = see the horses
• покормить козу = feed the goat

This probably suggests a real situation: maybe there are several horses at that place, but only one goat the speaker has in mind.

Because both mark the start of subordinate material.

1. сказала, что приедет...
   The comma before что is standard, because что introduces a subordinate clause:
   she said that she would come

2. ..., лишь бы снова увидеть...
   The comma before лишь бы separates another dependent phrase/clause expressing motivation or condition-like meaning.

Russian punctuation is often strongly tied to clause structure, so these commas are expected.

Yes, Russian word order is fairly flexible, but changing it changes the emphasis.

The given version is natural:

• приедет сюда ещё раз = neutral, smooth
• лишь бы снова увидеть лошадей = natural focus on again see the horses

Some alternatives are possible, for example:

• Моя подруга сказала, что ещё раз приедет сюда...
• ...лишь бы увидеть снова лошадей...

These are grammatically possible, but they sound different in rhythm or emphasis. The original sentence is a very natural, idiomatic choice.