Για να κοιμάμαι καλύτερα, αρκεί να πίνω λιγότερο καφέ το βράδυ.

In this sentence, για να introduces a purpose clause. It means in order to.

So:

• Για να κοιμάμαι καλύτερα = In order to sleep better

A very common pattern in Greek is:

• για να + verb

For example:

• Διαβάζω για να μάθω. = I study in order to learn.
• Πάω νωρίς για να προλάβω. = I go early so that I can make it.

In your sentence, the purpose comes first:

• Για να κοιμάμαι καλύτερα, ... This sets up the goal before giving the solution.

This is mainly about aspect, which is very important in Greek.

After να, Greek often uses either:

• the imperfective form, for repeated/habitual/ongoing actions
• the perfective form, for a single complete action

Here we have:

• να κοιμάμαι
• να πίνω

These are imperfective forms. That makes sense because the sentence talks about a general habit or regular pattern, not a one-time event:

• sleeping better in general
• drinking less coffee in the evenings as a habit

So the sentence is about something like:

• If I want to sleep better regularly, it is enough to drink less coffee in the evening.

If you wanted a more one-time, specific idea, Greek might use perfective forms such as:

• να κοιμηθώ
• να πιω

But that would change the feel of the sentence.

Because κοιμάμαι expresses a repeated or ongoing state/action, while κοιμηθώ points more to one completed instance of falling asleep / sleeping.

Compare the difference:

• Θέλω να κοιμάμαι καλύτερα.
  = I want to sleep better in general / as a regular situation

• Θέλω να κοιμηθώ καλά απόψε.
  = I want to sleep well tonight / this one time

In your sentence, the idea is not about one specific night. It is more like a lifestyle or habit statement, so κοιμάμαι is the natural choice.

For the same reason: πίνω here is imperfective, so it suggests a habitual action.

• να πίνω λιγότερο καφέ το βράδυ
  = to drink less coffee in the evening as a habit

If you said:

• να πιω λιγότερο καφέ το βράδυ

that would sound more like a single occasion or a more bounded action.

So in this sentence, the speaker means:

• reducing evening coffee in general not
• drinking less coffee on one particular evening

Αρκεί means:

• it is enough
• it suffices

It is very often used as an impersonal expression in Greek, especially in the pattern:

• αρκεί να + verb = it is enough to / one only needs to

So:

• αρκεί να πίνω λιγότερο καφέ το βράδυ = it is enough for me to drink less coffee in the evening = I only need to drink less coffee in the evening

It is singular because it is not really agreeing with a subject like I or you. It functions impersonally, similar to English it is enough.

Yes, very often.

Although the Greek literally works like it is enough that / it suffices to, in natural English you will often translate it as:

• I only need to...
• All I need to do is...

So this sentence can be understood as:

• To sleep better, I only need to drink less coffee in the evening.

That is a very natural way to take αρκεί να here.

Because καλύτερα is functioning as an adverb here.

It modifies the verb κοιμάμαι:

• κοιμάμαι καλύτερα = I sleep better

English also uses an adverb-like idea here:

• not a better sleep in this sentence
• but sleep better

A useful comparison:

• καλός = good
• καλά = well
• καλύτερα = better

So:

• κοιμάμαι καλά = I sleep well
• κοιμάμαι καλύτερα = I sleep better

Because καφέ here is the direct object of πίνω, so it must be in the accusative, not the nominative.

• nominative: ο καφές
• accusative: τον καφέ

After λιγότερο, the noun stays in the case required by the sentence. Since πίνω takes an accusative object, we get:

• πίνω λιγότερο καφέ = I drink less coffee

Also, coffee here is treated as a mass noun, just like in English.

Compare:

• πίνω λιγότερο καφέ = I drink less coffee
• πίνω λιγότερους καφέδες = I drink fewer coffees / fewer cups of coffee

So the sentence is using the mass-noun version.

Because καφέ is the accusative singular form.

The dictionary form is usually:

• ο καφές = coffee

But after a verb like πίνω, you need the object form:

• πίνω καφέ = I drink coffee

So:

• nominative: ο καφές
• accusative: τον καφέ / καφέ

This is a very common pattern with masculine nouns in -ές.

Greek very often uses the definite article in time expressions where English would not.

So:

• το βράδυ = in the evening / at night
• το πρωί = in the morning
• το μεσημέρι = at noon / in the afternoon depending on context

This is normal Greek usage. The article does not necessarily make it sound especially definite in the English sense.

So:

• πίνω καφέ το βράδυ = I drink coffee in the evening / at night

You will see this pattern a lot, and it is best learned as a standard time expression.

It can cover either, depending on context.

βράδυ is the part of the day after daytime, and in English the best translation may be:

• in the evening
• at night

In your sentence, either can work, but in the evening is often the most natural choice if the idea is about drinking coffee later in the day.

So:

• λιγότερο καφέ το βράδυ = less coffee in the evening

Because Greek usually omits subject pronouns when they are not needed.

The verb forms already show the person and number:

• κοιμάμαι = I sleep
• πίνω = I drink

So the I is already built into the verb.

Greek adds εγώ only when it wants emphasis or contrast, for example:

• Εγώ πίνω λιγότερο καφέ, αλλά αυτός όχι.
  = I drink less coffee, but he doesn’t.

In your sentence, no special emphasis is needed, so the pronoun is left out.

Because the sentence begins with a fronted clause:

• Για να κοιμάμαι καλύτερα, ...

This introductory purpose clause is separated from the main clause by a comma. That is standard and helps readability.

Structure:

• Για να κοιμάμαι καλύτερα = introductory purpose clause
• αρκεί να πίνω λιγότερο καφέ το βράδυ = main clause

So the comma marks that division.

Yes, Greek word order is relatively flexible, though some versions sound more natural than others.

The given sentence is very natural because it starts with the goal:

• Για να κοιμάμαι καλύτερα, αρκεί να πίνω λιγότερο καφέ το βράδυ.

You could also say:

• Αρκεί να πίνω λιγότερο καφέ το βράδυ για να κοιμάμαι καλύτερα.

This is also understandable, but it may feel slightly less neat because the purpose phrase comes at the end.

Greek often changes word order for:

• emphasis
• focus
• style
• information flow

So yes, other orders are possible, but the original is a very good, natural one.

Yes, in this construction για να is a fixed combination meaning in order to / so that.

So the first να is part of:

• για να

Then later you have a second να because of:

• αρκεί να

These are two separate constructions:

• για να κοιμάμαι καλύτερα
• αρκεί να πίνω λιγότερο καφέ το βράδυ

So the two να's are not a mistake or repetition. They belong to two different grammar patterns.

The sentence has two main parts:

1. Για να κοιμάμαι καλύτερα

   • purpose: in order to sleep better

2. αρκεί να πίνω λιγότερο καφέ το βράδυ

   • main statement: it is enough to drink less coffee in the evening

So the overall structure is:

• For goal X, it is enough to do Y.

More literally:

• In order for me to sleep better, it is enough for me to drink less coffee in the evening.

This is a very useful pattern in Greek.

Yes, but it changes the nuance.

• λιγότερο καφέ = less coffee
  This treats coffee as a mass noun and focuses on the overall amount.

• λιγότερους καφέδες = fewer coffees
  This treats coffees as countable units, often meaning cups/servings.

So:

• πίνω λιγότερο καφέ το βράδυ
  = I drink less coffee in the evening

• πίνω λιγότερους καφέδες το βράδυ
  = I drink fewer coffees in the evening

Both are possible, but the original sentence sounds more general and natural.

It sounds like a personal general statement.

Because of the first-person verb forms:

• κοιμάμαι
• πίνω

the speaker is talking about themselves. But because the aspect is imperfective, it does not sound like one single event. It sounds like a general pattern or habit:

• For me, if I want to sleep better, drinking less coffee in the evening is enough.

So it is personal, but also general/habitual in meaning.