Όταν πάω στην αγορά, πετυχαίνω συχνά τη φίλη μου.

Όταν can mean both when and whenever, depending on context.

In this sentence, the verb forms are in the present tense, so the meaning is usually whenever or when(ever) this happens regularly:

• Όταν πάω στην αγορά, πετυχαίνω συχνά τη φίλη μου.
• Whenever I go to the market, I often run into my friend.

So here Όταν introduces a time clause: it tells us at what time / under what recurring circumstance the main action happens.

Both πάω and πηγαίνω can mean I go in Modern Greek.

• πάω is very common in everyday speech
• πηγαίνω is also correct, and sometimes sounds a bit more formal or fuller

So these are both possible:

• Όταν πάω στην αγορά...
• Όταν πηγαίνω στην αγορά...

In this sentence, πάω is just the more natural everyday choice.

Because Greek usually uses the definite article where English often does too, and sometimes even where English might omit it.

• στην = σε + την
• σε means to / in / at
• την is the feminine singular accusative article the

So:

• στην αγορά = to the market / at the market

The noun αγορά is feminine, so it takes την in the accusative singular after σε.

στην is a contraction:

• σε + την = στην

This is extremely common in Greek.

Other similar forms are:

• στο = σε + το
• στον = σε + τον
• στις = σε + τις
• στους = σε + τους

So στην αγορά literally breaks down as:

• σε = to / in / at
• την αγορά = the market

The noun αγορά is feminine. In this case, the article shows the case more clearly than the noun ending does.

Here we have:

• την αγορά = accusative singular

For many feminine nouns, the nominative and accusative can look very similar or even identical in form, so the article helps you identify the case.

Here it is accusative because it comes after the preposition σε:

• σε την αγορά → στην αγορά

Prepositions like σε normally take the accusative in Modern Greek.

Because τη φίλη μου is the direct object of the verb πετυχαίνω.

• η φίλη μου = my friend as the subject
• τη φίλη μου = my friend as the object

Compare:

• Η φίλη μου έρχεται. = My friend is coming.
• Βλέπω τη φίλη μου. = I see my friend.

In your sentence, the speaker is the subject, and my friend is the person being encountered, so Greek uses the accusative:

• τη φίλη μου

Both are related, but τη is the usual written and spoken form before a consonant in everyday Modern Greek.

The full accusative feminine singular article is historically την, but in normal modern usage the final -ν is often dropped before many consonants:

• τη φίλη μου
• την αγορά also exists, but after σε it becomes στην αγορά

Very roughly:

• τη φίλη
• τη μητέρα
• την αδερφή may be kept more often depending on pronunciation and spelling conventions

You will often see the final -ν kept before vowels and certain consonants, but dropped elsewhere. This is a spelling/pronunciation issue, not a change in meaning.

Yes, πετυχαίνω has more than one meaning.

Common meanings include:

1. to succeed / achieve
2. to hit / reach
3. to come across / run into / meet by chance

In this sentence, it means:

• I often run into / come across my friend

So this is not a planned meeting; it suggests a chance encounter.

That is a very natural use of πετυχαίνω in Greek.

Greek word order is flexible, but this placement is very natural.

• πετυχαίνω συχνά τη φίλη μου

Here συχνά modifies the verb πετυχαίνω: it tells us how often the action happens.

You could also hear:

• συχνά πετυχαίνω τη φίλη μου
• τη φίλη μου την πετυχαίνω συχνά (more marked/emphatic)

So the chosen order is simply a common, neutral one.

Because the sentence describes a habitual or repeated situation.

• Όταν πάω στην αγορά = when/whenever I go to the market
• πετυχαίνω συχνά τη φίλη μου = I often run into my friend

Greek, like English, often uses the present tense for repeated actions or general truths.

If the sentence were about a future event, you would normally expect θα somewhere:

• Όταν θα πάω... is generally not the standard choice in this kind of sentence in Modern Greek
• More natural future phrasing would usually be something like:
  • Όταν πάω αύριο στην αγορά, ίσως πετύχω τη φίλη μου.

But in your sentence, this is a general routine, so present tense is exactly right.

Yes. In Greek, the weak possessive forms such as μου, σου, του, της, μας, σας, τους usually come after the noun.

So:

• η φίλη μου = my friend
• το σπίτι μου = my house
• οι γονείς μου = my parents

This is the normal Greek pattern, unlike English, where my comes before the noun.

Greek very often uses the definite article with possessives.

So the normal way to say my friend is:

• η φίλη μου (subject)
• τη φίλη μου (object)

Without the article, φίλη μου is possible in some contexts, but it often sounds more like direct address or a more special stylistic use:

• Φίλη μου, άκουσέ με. = My friend, listen to me.

In ordinary sentences, Greek strongly prefers the article with possessive expressions.

Yes, that is a very natural understanding.

Greek does not explicitly say there, but it is understood from στην αγορά. So the sentence naturally suggests:

• When I go to the market, I often run into my friend (there).

Greek often leaves this kind of location implied when it is already clear from the context.

Grammatically, στην αγορά means to the market / at the market, so it sounds like a definite place or a familiar kind of destination.

In real usage, it can mean:

• a specific market the speaker regularly goes to, or
• the market area / marketplace as a known place

So even though English might sometimes say to market or to the market, Greek naturally uses the article here:

• στην αγορά

That is the standard wording.