Ekki hvísla svona hratt; ég heyri þig varla.

Because Icelandic often forms a negative command with ekki + verb.

So:

• Ekki hvísla = Don’t whisper

This is the normal way to tell someone not to do something.

In form, hvísla is the infinitive, but after ekki it functions as a negative imperative.

That means:

• hvísla by itself = to whisper
• Ekki hvísla = don’t whisper

In a positive command, you would more often say:

• Hvíslaðu! = Whisper!

So Icelandic commonly uses the infinitive-looking form after ekki in negative commands.

Because commands usually leave out the subject when it is obvious.

So Ekki hvísla already means Don’t whisper (you).

You can think of it as similar to English imperatives:

• Stop
• Come here
• Don’t whisper

English usually omits you too, unless you want extra emphasis.

Svona means something like like this, like that, or very often so in everyday English.

In this sentence:

• svona hratt = so fast / that fast

It adds a conversational feeling. The speaker is not just saying fast, but this/that kind of fast.

Because hratt is being used adverbially.

• hraður = fast as an adjective
• hratt = fast / quickly as an adverb-like form

Icelandic often uses the neuter singular form of an adjective in this way.

So:

• hraður bíll = a fast car
• hann talar hratt = he speaks fast

Here, hratt describes how someone is whispering.

Because hvísla specifically means to whisper.

So the sentence is not just about speaking quickly; it is about speaking in a whisper quickly, which makes the person hard to hear.

That is why the second clause makes sense:

• ég heyri þig varla = I can barely hear you

Heyri is the 1st person singular present tense of heyra (to hear).

So:

• ég heyri = I hear
• þú heyrir = you hear
• við heyrum = we hear

The speaker is talking about what is happening right now, so the present tense is used.

Because þig is the accusative form of you, and heyra takes a direct object in the accusative.

Compare:

• þú = you as the subject
• þig = you as the object

So:

• Þú hvíslar. = You whisper.
• Ég heyri þig. = I hear you.

Since you are the one being heard, þig is the correct form.

Varla means hardly, barely, or scarcely.

So:

• ég heyri þig varla = I can barely hear you

It suggests that hearing is possible only with difficulty, or almost not at all.

That word order is very natural in Icelandic.

• Ég heyri þig varla sounds straightforward and idiomatic.

You may also see adverbs in slightly different positions in Icelandic, but the version here is a common one. Putting varla at the end gives it a nice final emphasis: I hear you — barely.

Because heyra means to hear, while hlusta means to listen.

That is an important difference:

• heyra = receive sound
• hlusta = actively listen

In this sentence, the problem is not that the speaker is refusing to listen. The problem is that the whisper is too fast and too quiet to be heard clearly, so heyra is the right verb.

Not for the grammar itself. It just links two closely connected ideas:

1. Ekki hvísla svona hratt
2. ég heyri þig varla

The second clause explains the reason for the first. You could also write them as two separate sentences:

• Ekki hvísla svona hratt. Ég heyri þig varla.

The semicolon simply makes the connection especially clear.

Yes, a few:

• hv in hvísla is usually pronounced much like kv in modern Icelandic.
• þ in þig is like the th in thin.
• ey in heyri is pronounced like Icelandic ei, roughly similar to ay in say, though not exactly the same as in English.
• Stress normally falls on the first syllable: HVÍS-la, HEY-ri, VAR-la.

Those are all sounds that English speakers often need a little practice with.