Μην ψιθυρίζεις τόσο πολύ· δεν σε ακούω καλά.

Because Greek uses μη(ν) to negate commands, requests, and similar subjunctive-type forms. Δεν negates ordinary statements.

So:

• Δεν ψιθυρίζεις = You are not whispering
• Μην ψιθυρίζεις = Don’t whisper / Stop whispering

Modern Greek does not normally use a negative imperative form the way English does; it uses μην + verb instead.

It comes from the dictionary form ψιθυρίζω, meaning to whisper.

Here, ψιθυρίζεις is the 2nd person singular non-past form: it is used when speaking to one person. After μην, it functions as the verb form used for a negative command.

So the sentence is addressed to one person: Don’t whisper so much.

This is an aspect question.

• Μην ψιθυρίζεις uses the imperfective / ongoing idea.
• Μην ψιθυρίσεις uses the perfective / one whole action idea.

So:

• Μην ψιθυρίζεις = Don’t keep whispering / Stop whispering so much
• Μην ψιθυρίσεις = Don’t whisper (more like a single event, or don’t whisper at all)

In this sentence, the speaker is reacting to an action that is already happening or happening repeatedly, so ψιθυρίζεις fits better.

It is not unusual at all. τόσο πολύ is a very common Greek combination.

• τόσο = so / this much
• πολύ = much / a lot

Together they strengthen the idea: so much, so heavily, or in context sometimes too much.

So Μην ψιθυρίζεις τόσο πολύ is a natural way to say Don’t whisper so much.

You could also hear:

• Μην ψιθυρίζεις τόσο
• Μην ψιθυρίζεις πολύ

But τόσο πολύ is perfectly normal and expressive.

Because ακούω takes a direct object for the person being heard.

• σε = you as a direct object
• σου = to you / your, which is not what the verb needs here

So:

• Σε ακούω = I hear you
• not Σου ακούω

Also, σε is an unstressed object pronoun, so it normally goes before the verb:

• δεν σε ακούω

That word order is standard in Greek.

Literally, καλά means well, but with verbs like hear, see, or understand, it often means well enough or clearly.

So:

• δεν σε ακούω καλά = I don’t hear you well
• very natural English translation: I can’t hear you clearly / well

It does not mean good in the sense of morally good here. It is just describing how well the hearing is happening.

Greek often leaves can / be able to unstated when the meaning is obvious from context.

So:

• δεν σε ακούω καλά literally = I don’t hear you well
• natural English = I can’t hear you well / clearly

If you wanted to make the idea of ability more explicit, Greek could say:

• Δεν μπορώ να σε ακούσω καλά

But in everyday speech, δεν σε ακούω καλά is completely natural.

That is the Greek άνω τελεία, the raised dot.

It works roughly like an English semicolon or sometimes a colon. It marks a stronger pause than a comma.

So here:

• Μην ψιθυρίζεις τόσο πολύ· δεν σε ακούω καλά.

means something like:

• Don’t whisper so much; I can’t hear you well.

A very common beginner confusion is this:

• Greek question mark = ;
• Greek raised dot = ·

So the mark in this sentence is not a question mark.

It is singular and normally informal, because it uses:

• ψιθυρίζεις = you singular
• σε = you singular object

If you were talking to more than one person, or speaking politely to one person, Greek would usually use the plural form:

• Μην ψιθυρίζετε τόσο πολύ· δεν σας ακούω καλά.

So this sentence is the one-person, informal version.

A rough pronunciation guide is:

• Μην = meen
• ψιθυρίζεις = psee-thee-REE-zees
• τόσο = TO-so
• πολύ = po-LEE
• δεν σε ακούω καλά = then se a-KOO-o ka-LA

A few useful points:

• ψ at the beginning is pronounced ps, not just s
• θ sounds like th in think
• Stress goes where the accent mark is:
  • ψιθυρίζεις
  • ακούω
  • καλά

For many English speakers, the hardest word here is ψιθυρίζεις, mainly because of the initial ψ and the θ sound in the middle.