Πρόσεχε μην ξεχάσεις το φλας και μην πατήσεις την κόρνα από νεύρα, γιατί το παιδί στο πίσω κάθισμα κοιμάται.

Both are imperatives of προσέχω (to be careful / pay attention), but they do not feel exactly the same.

• Πρόσεχε is the imperfective imperative. It often means be careful, watch it, keep paying attention, or make sure you don't...
• Πρόσεξε is the perfective imperative. It often sounds more like watch out! or pay attention right now to a specific thing.

In this sentence, Πρόσεχε fits well because the speaker is giving ongoing caution while driving:
Be careful not to forget the turn signal and not to hit the horn...

So Πρόσεχε suggests a more continuous attitude of care.

This is a very common Greek pattern.

After verbs like προσέχω, Greek often uses:

• μη(ν)
  • subjunctive

So:

• μην ξεχάσεις = not to forget
• μην πατήσεις = not to press / not to hit

Even though ξεχάσεις and πατήσεις may look like past forms to an English speaker, here they are subjunctive, not past tense.

So:

• Πρόσεχε μην ξεχάσεις... = Be careful not to forget...
• Πρόσεχε μην πατήσεις... = Be careful not to press...

This is one of the standard ways Greek expresses warnings.

Because each negative idea is stated separately:

• μην ξεχάσεις το φλας
• και μην πατήσεις την κόρνα

Greek usually repeats μην when two negative subjunctive clauses are linked like this. It keeps the sentence clear and natural.

In English, we might say:
Be careful not to forget the signal and not to hit the horn...

Greek prefers to mark both verbs clearly with μην.

They are aorist subjunctive, 2nd person singular.

From:

• ξεχνάω / ξεχνώ → να ξεχάσεις
• πατάω / πατώ → να πατήσεις

After μην, Greek uses the same subjunctive form without να:

• μην ξεχάσεις
• μην πατήσεις

The aorist subjunctive here usually refers to a single action:

• forget once
• press once

That is why it works well in warnings about specific actions.

Το φλας means the turn signal / indicator / blinker.

It is a loanword, and in everyday Greek φλας is very common in driving contexts.

A few useful points:

• It is neuter: το φλας
• The form usually stays the same in singular: το φλας
• In speech, Greeks may use it just like English speakers use signal or blinker

So μην ξεχάσεις το φλας means don't forget the turn signal or more naturally don't forget to use the turn signal.

Greek uses the definite article much more often than English.

So Greek naturally says:

• το φλας
• την κόρνα
• το παιδί
• το πίσω κάθισμα

Even where English might say:

• don't forget to signal
• don't hit the horn
• a child in the back seat is sleeping

Greek often prefers the article when referring to a concrete, known thing in the situation.

So this is normal Greek usage, not something you need to translate word-for-word into English.

Την κόρνα is accusative singular feminine, because it is the direct object of πατήσεις.

Dictionary form:

• η κόρνα = the horn

As a direct object:

• πατάω την κόρνα = I press the horn / honk the horn

So the article changes:

• nominative: η κόρνα
• accusative: την κόρνα

This is very normal Greek object marking.

Yes. Literally it means press the horn, and this is a very natural Greek expression.

So:

• πατάω την κόρνα = I honk / I hit the horn / I press the horn

Greek often expresses this action through the physical motion of pressing it.

Από νεύρα is an idiomatic expression meaning something like:

• out of irritation
• out of anger
• because you're annoyed
• in frustration

Literally, νεύρα means nerves, but in everyday Greek it often refers to anger, tension, irritation, bad temper.

So:

• μην πατήσεις την κόρνα από νεύρα = don't hit the horn out of irritation / in frustration

Very common everyday expression:

• Έχω νεύρα = I'm irritated / I'm in a bad mood / I'm angry

Because Greek commonly uses τα νεύρα in the plural to talk about someone's nerves, irritation, or temper.

Some common expressions:

• Έχω νεύρα = I'm irritated / angry
• Μου έσπασε τα νεύρα = He/She got on my nerves
• Από νεύρα = out of irritation

So although English often uses a singular abstract noun like anger or frustration, Greek very naturally uses the plural νεύρα.

It can mean both, depending on context.

Here it means because:

• ..., γιατί το παιδί στο πίσω κάθισμα κοιμάται.
• ..., because the child in the back seat is sleeping.

When γιατί introduces a reason, it means because.
When it introduces a question, it means why.

Compare:

• Γιατί γελάς; = Why are you laughing?
• Γελάω γιατί είμαι χαρούμενος. = I'm laughing because I'm happy.

So in your sentence, it is clearly the conjunction because.

Yes. Στο is a contraction of:

• σε
  • το → στο

So:

• στο πίσω κάθισμα = in/on the back seat

Breaking it down:

• σε = in / on / at / to
• το = the
• πίσω = back / rear
• κάθισμα = seat

So literally: in the back seat.

These contractions are extremely common:

• στο = σε το
• στη = σε τη / στην
• στον = σε τον

Because πίσω is the normal everyday word for back / rear in this kind of context.

So:

• πίσω κάθισμα = back seat

More formal or technical words exist, but πίσω is what you would usually hear in ordinary speech.

You can think of it as the natural colloquial choice.

Because the child is currently sleeping.

• κοιμάται = he/she is sleeping or sleeps

In context, it clearly means is sleeping right now.

Greek present tense often covers both:

• simple present
• present continuous

So το παιδί ... κοιμάται can mean:

• the child sleeps
• the child is sleeping

Here the situation makes is sleeping the natural translation.

Greek word order is more flexible than English, but the chosen order sounds natural and clear.

• το παιδί = the topic/person being talked about
• στο πίσω κάθισμα = adds location
• κοιμάται = gives the main information

So the sentence flows like:
the child in the back seat is sleeping

You could rearrange parts for emphasis, but this version is neutral and natural.

For example:

• Το παιδί κοιμάται στο πίσω κάθισμα also works.
• But Το παιδί στο πίσω κάθισμα κοιμάται nicely highlights the child in the back seat as the reason for the warning.

Not exactly in the strongest English sense.

Watch out! in English often sounds like an immediate danger warning.
Here Πρόσεχε is more like:

• Be careful
• Be careful not to...
• Make sure you don't...

So although watch out is not impossible in some contexts, be careful is the better fit here.

Because Modern Greek does not use the infinitive the way English does.

Instead, Greek normally uses:

• να
  • subjunctive
• or μη(ν)
  • subjunctive for negative clauses

So where English says:

• to forget
• to press

Greek says:

• να ξεχάσεις
• να πατήσεις
• or after a negative trigger: μην ξεχάσεις, μην πατήσεις

This is one of the biggest structural differences between English and Greek.

It is informal singular.

You can tell from the verb forms:

• Πρόσεχε
• ξεχάσεις
• πατήσεις

These are all addressed to one person in the familiar you form.

If the speaker were addressing more than one person, the forms would be different.

So this sounds like one person speaking to another person directly, probably in a car.

It sounds like a practical, mildly emotional reminder said to a driver:

• Be careful not to forget the turn signal, and don't lean on the horn out of irritation, because the kid in the back seat is asleep.

So the tone is:

• conversational
• cautioning
• slightly annoyed or protective
• very natural in everyday speech

The Greek does not sound especially formal or literary; it sounds like something a real person might say in a car.