Η φίλη μου έχει μια μελανιά στον αστράγαλο, γιατί χτες γύρισε το πόδι της στο πάρκο.

Yes. η φίλη μου means my friend, and it specifically refers to a female friend.

• η φίλη = the female friend
• μου = my

In Greek, short possessive words like μου usually come after the noun, not before it. So Greek says literally:

• the friend my = my friend

If you wanted a male friend, you would say:

• ο φίλος μου = my male friend

So the article and noun ending tell you the gender:

• η φίλη = female friend
• ο φίλος = male friend

μια μελανιά means a bruise.

• μια = a / one
• μελανιά = bruise

Greek often uses the indefinite article where English uses a. You could sometimes omit it in Greek, but here μια μελανιά sounds natural and complete.

Also, μελανιά is a feminine noun, so it takes the feminine form of the indefinite article:

• μια μελανιά = a bruise

Compare:

• ένας φίλος = a male friend
• μια φίλη = a female friend
• ένα παιδί = a child

μελανιά means bruise.

It refers to the dark mark on the skin you get after hitting yourself or injuring yourself.

Related vocabulary:

• μελανιά = bruise
• χτύπημα = hit / blow / injury
• πληγή = wound
• πόνος = pain

So έχει μια μελανιά means she has a bruise.

στον is a contraction of:

• σε + τον = στον

Here:

• σε = in / at / on / to
• τον = the (masculine accusative singular)

So:

• στον αστράγαλο = on the ankle / at the ankle

The noun αστράγαλος is masculine:

• ο αστράγαλος = the ankle
• τον αστράγαλο = the ankle (accusative form)

After σε, Greek uses the accusative, so:

• σε τον αστράγαλο → στον αστράγαλο

This is very common:

• στον δρόμο = in the street
• στον γιατρό = to the doctor
• στον αστράγαλο = on the ankle

That is a very common question. γιατί can mean both:

• why?
• because

You tell the difference from the sentence structure and punctuation.

Here:

• ..., γιατί χτες γύρισε το πόδι της στο πάρκο.
• This is giving the reason, so γιατί = because

Examples:

• Γιατί έφυγες; = Why did you leave?
• Έφυγα γιατί ήμουν κουρασμένος. = I left because I was tired.

So in your sentence, γιατί introduces the explanation for the bruise.

Yes. χτες means yesterday, and it is the same as χθες.

Both forms are used in modern Greek:

• χτες
• χθες

χτες is very common in everyday speech and writing.
χθες is also correct and may look a little more formal or traditional to learners because of the spelling.

So:

• χτες γύρισε το πόδι της = yesterday she twisted her foot/leg

Normally, yes:

• γυρίζω can mean turn, go back, return, or spin

But in this sentence, γύρισε το πόδι της is an idiomatic expression. It means:

• she twisted her foot/leg
• often, more naturally in English: she twisted her ankle

So the verb keeps its basic idea of turning, but in the context of injury it means that the foot/leg turned awkwardly.

γύρισε is the aorist form, so it refers to a completed action in the past:

• γυρίζει = she turns / is turning
• γύρισε = she turned / twisted

Because Greek often uses πόδι in expressions like this.

• πόδι can mean leg or foot, depending on context
• In injury contexts, γυρίζω το πόδι μου often means I twist my foot/ankle

So although the sentence literally says:

• she twisted her foot/leg

the natural English meaning may be:

• she twisted her ankle

That is especially likely here because the bruise is στον αστράγαλο (on the ankle).

So this is a good example of translating by meaning, not word-for-word.

της here means her.

So:

• το πόδι = the foot / leg
• της = her

Together:

• το πόδι της = her foot / her leg

Greek commonly uses:

• definite article + noun + possessive clitic

So instead of putting a separate word before the noun like English does, Greek often says something like:

• το βιβλίο μου = my book
• η φίλη μου = my friend
• το πόδι της = her foot/leg

This is the normal Greek way to show possession.

In Greek, body parts normally take the definite article when possession is shown.

So Greek prefers:

• το πόδι της = her foot/leg
• το χέρι μου = my hand
• το κεφάλι του = his head

This is more natural than leaving out the article.

English says:

• her foot

Greek says literally:

• the foot her

That pattern is very common and very important to get used to.

αστράγαλο is in the accusative singular.

The dictionary form is:

• ο αστράγαλος = the ankle

After the preposition σε, Greek uses the accusative:

• σε τον αστράγαλο = on the ankle / at the ankle

Then that contracts to:

• στον αστράγαλο

So the forms are:

• ο αστράγαλος = nominative
• τον αστράγαλο = accusative

This is why you see αστράγαλο, not αστράγαλος.

They are in different tenses:

• έχει = has → present tense
• γύρισε = twisted / turned → aorist (simple past)

So the sentence combines:

1. a present result:
   • Η φίλη μου έχει μια μελανιά...
   • My friend has a bruise...
2. a past cause:
   • γιατί χτες γύρισε το πόδι της...
   • because yesterday she twisted her foot/ankle...

This is very natural:

• present situation now
• past event that caused it

Yes, Greek word order is more flexible than English word order.

The sentence as given is perfectly natural:

• Η φίλη μου έχει μια μελανιά στον αστράγαλο, γιατί χτες γύρισε το πόδι της στο πάρκο.

But Greek can often move things around for emphasis. For example, parts like χτες or στο πάρκο could sometimes appear in a different place.

Still, the given order is easy and natural:

• first the main fact: My friend has a bruise on her ankle
• then the reason: because yesterday she twisted her foot/ankle in the park

So even if Greek allows flexibility, this sentence is a good standard model.

It can mean either in the park or at the park, depending on context.

• στο = σε + το
• πάρκο = park

So:

• στο πάρκο = in the park / at the park

In English, in the park is probably the most natural translation here:

• because yesterday she twisted her ankle in the park

But at the park could also work in some contexts.

Yes, it is natural Greek.

A native speaker could also express the same idea in slightly different ways, for example by using χθες instead of χτες, or by choosing a different connector like επειδή instead of γιατί. But the sentence you have is perfectly normal and understandable.

One small thing to notice is that Greek often says:

• γύρισε το πόδι της where English may prefer:
• she twisted her ankle

So the Greek is natural even if the most natural English translation is a little less literal.