Δεν μπορώ να καταπιώ αυτό το χάπι χωρίς νερό, οπότε ρουφάω λίγο τσάι πρώτα.

In Greek, μπορώ is normally followed by να + a verb.

• μπορώ να... = I can...
• δεν μπορώ να... = I can’t...

So:

• Δεν μπορώ να καταπιώ = I can’t swallow

The να is very important here. It introduces the following verb in the subordinate clause.

This is a very common learner question. After μπορώ να, Greek often chooses between:

• an imperfective form, for ongoing/repeated action
• a perfective form, for a single complete action

Here, καταπιώ is the perfective form of καταπίνω. It focuses on one complete act of swallowing the pill.

• Δεν μπορώ να καταπιώ αυτό το χάπι
  = I can’t swallow this pill
  (one specific swallowing event)

If you said:

• Δεν μπορώ να καταπίνω χάπια
  it would sound more like I can’t swallow pills in general / habitually.

So καταπιώ fits better because we are talking about swallowing one particular pill.

No. It may look like a future-type form, but here it is not future.

Greek uses the same stem/form in several places:

• after να
• after θα
• in certain dependent clauses

So in:

• να καταπιώ

the form is not future tense. It is the perfective non-past form used after να.

Compare:

• Θα καταπιώ το χάπι. = I will swallow the pill.
• Μπορώ να καταπιώ το χάπι. = I can swallow the pill.

Same verb form, different meaning because of θα vs να.

Because that is the normal Greek pattern with demonstratives.

Greek usually says:

• αυτό το βιβλίο = this book
• εκείνο το σπίτι = that house

So the structure is:

• demonstrative + article + noun

Here:

• αυτό = this
• το = the
• χάπι = pill

All three agree in gender, number, and case:

• αυτό το χάπι = this pill

This is normal Greek, even though English does not use both this and the together.

Because νερό here means water in a general sense, not a specific water.

• χωρίς νερό = without water
• χωρίς το νερό would mean something more like without the water
  (some specific water already known in context)

Greek often omits the article with mass nouns when speaking generally:

• πίνω καφέ = I drink coffee
• θέλω ψωμί = I want bread
• χωρίς νερό = without water

So χωρίς νερό is exactly what you would expect here.

Here οπότε means so, therefore, or as a result.

In this sentence:

• Δεν μπορώ να καταπιώ αυτό το χάπι χωρίς νερό, οπότε ρουφάω λίγο τσάι πρώτα.
• I can’t swallow this pill without water, so I sip a little tea first.

It links the first clause to the consequence in the second clause.

Be aware that οπότε can also mean when in some contexts, but here it clearly means so / therefore.

Yes, ρουφάω literally means to suck, to slurp, or to draw in. Depending on context, it can sound like:

• sip
• slurp
• suck down

So ρουφάω λίγο τσάι is not the most neutral way to say I drink a little tea. It gives a more physical sense of drawing the tea in, maybe in small quick sips.

A more neutral verb would be:

• πίνω λίγο τσάι πρώτα = I drink a little tea first

So a learner might notice that ρουφάω is slightly more vivid or colloquial than plain πίνω.

Because λίγο works very naturally as a little / some with mass nouns.

• λίγο τσάι = a little tea
• λίγο νερό = a little water
• λίγο ψωμί = a little bread / some bread

You do not need an article here, because τσάι is being used as an uncountable quantity.

• λίγο το τσάι would not fit this meaning.
• λίγο από τσάι is possible only in more specific contexts, like a little from the tea, but not as the normal way to say a little tea.

So λίγο τσάι is the standard phrasing.

Greek word order is flexible, and adverbs like πρώτα can often move around.

Here:

• ρουφάω λίγο τσάι πρώτα

means I sip a little tea first.

Putting πρώτα at the end is very natural. It highlights the sequence of actions.

You could also hear:

• Πρώτα ρουφάω λίγο τσάι.
• Ρουφάω πρώτα λίγο τσάι.

All are possible, but the version in your sentence is smooth and idiomatic.

Greek present tense is often used just like English present for what someone does in the current situation.

Here, the speaker means something like:

• I can’t swallow this pill without water, so I take a little tea first.

It describes the action as the speaker’s present response or usual way of handling the situation.

Greek does this very naturally with the present tense:

• δεν μπορώ..., οπότε κάνω...
• I can’t..., so I do...

It does not have to mean a repeated habit only; it can also describe what the speaker is doing in this situation.

Yes. Χάπι is the everyday word for pill or tablet.

In many contexts:

• χάπι = pill
• χάπι / δισκίο = tablet

Δισκίο is more formal or medical. Χάπι is the ordinary conversational word, so it fits this sentence well.

Because in Greek, δεν normally goes directly before a finite verb in ordinary negation.

So:

• μπορώ = I can
• δεν μπορώ = I can’t

Then the rest follows:

• δεν μπορώ να καταπιώ...

This is the standard placement for negation in a sentence like this.

Most of it is perfectly natural:

• Δεν μπορώ να καταπιώ αυτό το χάπι χωρίς νερό sounds very natural.

The part that may stand out slightly is:

• ρουφάω λίγο τσάι πρώτα

because ρουφάω is more vivid than neutral πίνω. A native speaker might very well say:

• ...οπότε πίνω λίγο τσάι πρώτα.

That would sound more neutral: so I drink a little tea first.

So the sentence is understandable and mostly natural, but ρουφάω gives it a slightly stronger, more physical nuance.