Προσανατολίζομαι με την πυξίδα.

Because προσανατολίζομαι is the mediopassive form of the verb.

In Modern Greek, many verbs appear in this kind of form even when the meaning is active in English. Here it means something like:

• I orient myself
• I find my bearings
• I navigate

So although it looks passive to an English speaker, in this sentence it is used with an active meaning.

The basic pair is:

• προσανατολίζω = I orient something / I direct something
• προσανατολίζομαι = I orient myself / I get oriented

So the sentence uses the form that fits the idea of the speaker finding direction for themselves.

In this sentence, προσανατολίζομαι means something like:

• I orient myself
• I determine direction
• I find my bearings
• I navigate

With με την πυξίδα, the full idea is that the speaker is using a compass to work out direction.

Depending on context, προσανατολίζομαι can also be used more abstractly, for example:

• προσανατολίζομαι επαγγελματικά = I orient myself professionally / I decide my professional direction

But in your sentence, it is the literal, physical sense.

Με here means with and introduces the means or tool used to do something.

So:

• με την πυξίδα = with the compass / using the compass

This is very common in Greek:

• γράφω με μολύβι = I write with a pencil
• πάω με το λεωφορείο = I go by bus
• κόβω με το μαχαίρι = I cut with the knife

So in your sentence, με tells you what instrument helps the speaker orient themselves.

Because after με, Modern Greek uses the accusative case.

So:

• η πυξίδα = the compass (nominative)
• την πυξίδα = the compass (accusative)

This is one of the important differences from Ancient Greek: in Modern Greek, many prepositions, including με, are followed by the accusative.

That is why the sentence says:

• με την πυξίδα

not:

• με τη πυξίδα in very careful standard spelling? Actually με την πυξίδα is fully correct, while με τη πυξίδα may occur in speech-like writing but is less standard before this word.
• not a genitive or dative form either

Yes, you often can say με πυξίδα, and it would mean with a compass.

The version with the article, με την πυξίδα, usually sounds more like:

• with the compass
• using the compass

It can refer to:

1. a specific compass already known in the context, or
2. the compass as the practical tool being used

Compare:

• Προσανατολίζομαι με πυξίδα. = I orient myself using a compass / by compass
• Προσανατολίζομαι με την πυξίδα. = I orient myself with the compass

In many everyday contexts, both are possible, but the article makes it sound a little more definite.

A simple pronunciation guide is:

• Προσανατολίζομαι ≈ pro-sa-na-to-LEE-zo-me
• με ≈ meh
• την ≈ teen
• πυξίδα ≈ peek-SEE-tha

A few useful notes:

• The stress in Προσανατολίζομαι falls on λί.
• The stress in πυξίδα falls on ξί.
• ξ sounds like ks.
• δ in Modern Greek sounds like the th in this, not like English d.

A more connected approximation would be:

prosanato-LEE-zome meh teen peek-SEE-tha

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

The neutral order here is:

• Προσανατολίζομαι με την πυξίδα.

But you could also say:

• Με την πυξίδα προσανατολίζομαι.

This gives more emphasis to με την πυξίδα.

In many contexts, the original version is the most natural if you are simply stating the fact. Greek often changes word order for emphasis, contrast, or style, without changing the core meaning.

Yes, προσανατολίζομαι is in the present tense.

In Modern Greek, the present tense can mean:

• something happening right now
• something habitual
• something generally true

So the sentence could mean:

• I am orienting myself with the compass
• I use the compass to orient myself
• I navigate by means of the compass

The exact interpretation depends on context.

Common forms would be:

• Προσανατολίστηκα με την πυξίδα. = I oriented myself / found my bearings with the compass.
• Θα προσανατολιστώ με την πυξίδα. = I will orient myself with the compass.

This helps show an important pattern in Modern Greek:

• present/imperfective: προσανατολίζομαι
• aorist/perfective: προσανατολίστηκα
• future with θα: θα προσανατολιστώ

Learners often notice that the past and future forms may look quite different from the present.

Yes, πυξίδα is the normal word for compass.

It is a feminine noun, which is why the article is:

• η πυξίδα = the compass
• την πυξίδα = the compass (accusative)

A useful mini-paradigm is:

• η πυξίδα = nominative singular
• της πυξίδας = genitive singular
• την πυξίδα = accusative singular

So the article and noun ending both fit a feminine noun.

Yes, a Greek speaker could say it, and it is grammatically correct.

Depending on context, other natural alternatives might also appear, for example:

• Βρίσκω τον προσανατολισμό μου με την πυξίδα. = I find my bearings with the compass.
• Χρησιμοποιώ την πυξίδα για να προσανατολιστώ. = I use the compass to orient myself.

Your original sentence is concise and perfectly understandable. It sounds a bit more formal or textbook-like than the most casual everyday phrasing, but it is absolutely good Greek.