Αγόρασα λευκή μπογιά και ένα καινούριο πινέλο, γιατί η παλιά μπογιά είχε σχεδόν τελειώσει.

Because the verb ending already tells you the subject.

• αγόρασα = I bought
• The ending -α here shows first person singular.

Greek often leaves out subject pronouns like εγώ (I) unless the speaker wants emphasis or contrast.

So:

• Αγόρασα λευκή μπογιά = I bought white paint
• Εγώ αγόρασα λευκή μπογιά would sound more like I bought white paint (as opposed to someone else).

Because adjectives in Greek must agree with the noun they describe in gender, number, and case.

In this sentence:

• μπογιά (paint) is feminine singular
• πινέλο (paintbrush) is neuter singular

So the adjectives change form to match:

• λευκή μπογιά = white paint
  
  • λευκή is feminine singular
• παλιά μπογιά = old paint
  
  • παλιά is feminine singular
• καινούριο πινέλο = new paintbrush
  
  • καινούριο is neuter singular

This is very normal in Greek and one of the first things learners notice.

Greek uses articles differently depending on whether something is being presented as indefinite or definite.

In your sentence:

• λευκή μπογιά = white paint
  No article is possible here and sounds natural, especially with materials or substances.
• ένα καινούριο πινέλο = a new paintbrush
  ένα is the indefinite article (a/an) for neuter singular nouns.
• η παλιά μπογιά = the old paint
  η is the definite article (the) for feminine singular nouns.

So the sentence distinguishes between:

• some white paint
• a new paintbrush
• the old paint (specific paint already known in the situation)

There are two main cases here: accusative and nominative.

Accusative: direct objects of αγόρασα

These are the things that were bought:

• λευκή μπογιά
• ένα καινούριο πινέλο

They are in the accusative, although for these particular nouns the forms look the same as the nominative.

Nominative: subject of είχε τελειώσει

• η παλιά μπογιά is the subject of had almost run out / had almost finished

So:

• Αγόρασα ... → I bought ... → object in accusative
• η παλιά μπογιά είχε σχεδόν τελειώσει → the old paint had almost run out → subject in nominative

Yes, γιατί can mean both because and why, depending on context.

In this sentence, it means because:

• ..., γιατί η παλιά μπογιά είχε σχεδόν τελειώσει.
• ..., because the old paint had almost run out.

It can also appear in questions:

• Γιατί αγόρασες μπογιά; = Why did you buy paint?

So learners have to rely on context and punctuation:

• in a statement, γιατί often means because
• in a question, it usually means why

Because είχε τελειώσει is the pluperfect (past perfect): had finished / had run out.

Here the speaker is describing two past actions, and one happened earlier than the other:

1. the old paint had almost run out
2. then the speaker bought new paint and a brush

So Greek uses:

• είχε τελειώσει = had finished / had run out

If you said:

• η παλιά μπογιά τελείωσε

that would mean:

• the old paint ran out / finished

That is a simple past statement, but it does not show the same clear earlier-than-the-buying relationship as strongly as είχε τελειώσει does.

σχεδόν means almost.

So:

• είχε σχεδόν τελειώσει = had almost run out / had almost been used up

The word τελειώνω / τελειώνω κάτι / τελειώνω often means finish, but with things like paint, food, money, etc., it can naturally mean be used up / run out.

So in this context:

• η μπογιά είχε σχεδόν τελειώσει does not mean someone was “finishing” the paint as a task
• it means the paint supply was nearly gone

Because Greek often places adverbs like σχεδόν before the main verb element they modify.

Here:

• είχε σχεδόν τελειώσει

literally looks like:

• had almost finished

This placement is very natural in Greek.

You may also see adverbs in slightly different positions in other sentences, but this one is standard and idiomatic.

They are close in meaning, but not always identical in feel.

• καινούριος / καινούριο usually means new, often in the sense of brand new
• νέος / νέο can also mean new, but it can additionally mean young depending on context

So:

• ένα καινούριο πινέλο = a new/brand-new paintbrush
• ένα νέο πινέλο can also mean a new paintbrush, but καινούριο often feels a bit more concrete and everyday in this kind of sentence

Both are common; καινούριο is very natural here.

Mostly, this is just something you learn with each noun.

Greek nouns have grammatical gender:

• η μπογιά = feminine
• το πινέλο = neuter

This gender is grammatical, not biological. Objects do not have “real” gender, but the grammar treats the nouns as masculine, feminine, or neuter.

That matters because:

• the article changes: η, το, ο
• the adjective changes: λευκή, καινούριο, παλιά

A good habit is to learn every new noun together with its article:

• η μπογιά
• το πινέλο

Because the second part gives the reason for the first part.

The sentence has two parts:

1. Αγόρασα λευκή μπογιά και ένα καινούριο πινέλο
2. γιατί η παλιά μπογιά είχε σχεδόν τελειώσει

The comma helps separate the main statement from the reason clause.

In English, this is similar to:

• I bought white paint and a new paintbrush, because the old paint had almost run out.

Punctuation rules do not always match perfectly between Greek and English, but the comma here is completely normal.

Yes. Greek word order is more flexible than English, although not completely free.

The basic sentence:

• Αγόρασα λευκή μπογιά και ένα καινούριο πινέλο, γιατί η παλιά μπογιά είχε σχεδόν τελειώσει.

is neutral and natural.

But Greek could move things around for emphasis, for example:

• Γιατί η παλιά μπογιά είχε σχεδόν τελειώσει, αγόρασα λευκή μπογιά και ένα καινούριο πινέλο.

This still means the same thing, but the focus shifts slightly toward the reason first.

So yes, Greek allows more movement than English, but the original version is a very standard way to say it.