Κι ας λυπάμαι που δεν έχω πολύ χρόνο, θέλω να καθίσω λίγο μαζί σας.

Here κι ας is an idiomatic concessive expression. It means something like even though, although, or be that as it may.

So:

Κι ας λυπάμαι που δεν έχω πολύ χρόνο
= Even though I’m sorry that I don’t have much time

It is not meant literally as and let... here. As a fixed pattern, κι ας + verb often introduces a contrast.

Κι is just the short form of και.

It is extremely common before a word beginning with a vowel, especially in natural speech and normal writing:

• κι ας
• κι εγώ
• κι εκείνος

There is no difference in meaning here. Κι simply sounds smoother before ας.

Here λυπάμαι means I’m sorry or I regret.

Depending on context, λυπάμαι can mean:

• I am sorry
• I feel sad
• I regret

In this sentence, it clearly has the sense of polite regret:

λυπάμαι που δεν έχω πολύ χρόνο
= I’m sorry that I don’t have much time

After verbs of emotion or reaction, Greek very often uses που to introduce the thing that causes the feeling.

So:

• Λυπάμαι που έφυγες = I’m sorry that you left
• Χαίρομαι που ήρθες = I’m glad that you came

In your sentence:

λυπάμαι που δεν έχω πολύ χρόνο
= I’m sorry that I don’t have much time

Here που is working like that in English.

Yes, it is in a subjunctive environment, because ας can introduce the subjunctive.

What may confuse learners is that in Modern Greek, the subjunctive often does not look different from the present indicative. The subjunctive is usually signaled by particles such as να or ας, not by a special verb ending.

So in:

ας λυπάμαι

the form λυπάμαι looks the same as the indicative, but it is understood within the ας construction.

Because χρόνο is masculine accusative singular, and the matching form of πολύς there is πολύ.

The adjective πολύς changes form:

• masculine nominative: πολύς
• feminine nominative: πολλή
• neuter nominative/accusative: πολύ
• masculine accusative: πολύ

So:

• πολύς χρόνος = a lot of time as subject
• έχω πολύ χρόνο = I have a lot of time as object

That is why πολύ is correct here.

Because Greek, like English, often leaves out the article when talking about an indefinite quantity.

So:

• έχω πολύ χρόνο = I have a lot of time
• δεν έχω πολύ χρόνο = I don’t have much time

Adding an article would change the feel and would usually not be the normal way to express this idea.

Because θέλω is normally followed by να + subjunctive in Modern Greek.

So:

• θέλω να φύγω = I want to leave
• θέλω να μιλήσω = I want to speak
• θέλω να καθίσω = I want to sit down / sit

This is the regular pattern. Greek does not use an infinitive here the way English does.

This is an aspect choice.

να καθίσω uses the aorist subjunctive, which presents the action as a whole event: to sit down / to sit for a bit.

If you used a present-type form such as να κάθομαι, it would suggest something more ongoing, repeated, or habitual.

In this sentence, the speaker means a single, limited action:

I want to sit with you for a little while

So να καθίσω is the natural choice.

They are very close in meaning, and in many contexts both can mean sit down or sit.

But there is a difference in style:

• κάτσω is more everyday and colloquial
• καθίσω sounds a bit more neutral or slightly more careful/polite

Since this sentence has a polite tone, καθίσω fits very well.

Here λίγο means a little, for a bit, or for a little while.

It is modifying the verb:

να καθίσω λίγο μαζί σας
= to sit with you for a little while

So it does not mean that the person will sit only partially or weakly; it refers to duration.

μαζί σας means with you or together with you.

• μαζί = together / with
• σας = you plural, or polite singular you

So the phrase is polite and can mean either:

• with you all
• with you when speaking formally to one person

Because σας is used for:

• you plural
• you formal singular

By contrast, σου is informal singular.

So:

• μαζί σου = with you to one person informally
• μαζί σας = with you to several people, or to one person politely

This sentence sounds polite, so σας makes good sense.

The comma separates the opening concessive clause from the main clause.

Structure:

• Κι ας λυπάμαι που δεν έχω πολύ χρόνο, = subordinate concessive idea
• θέλω να καθίσω λίγο μαζί σας. = main statement

In English, you would also normally separate this kind of opening clause:

Even though I’m sorry that I don’t have much time, I want to sit with you for a little while.

So the comma is very natural here.