Ég skil þetta auðveldlega þegar þú talar hægt.

Because skilja is the infinitive form, meaning to understand.

In the sentence, the verb is conjugated for 1st person singular (I), so:

• að skilja = to understand
• ég skil = I understand

So Ég skil þetta means I understand this.

Skil is the present-tense form of skilja.

A very common pattern in Icelandic is:

• ég skil = I understand
• þú skilur = you understand
• hann/hún/það skilur = he/she/it understands

So in this sentence, skil is simply the verb understand matched with ég.

Þetta means this, but in many contexts it can also feel like English this or it, depending on what is being referred to.

Here it is the direct object of skil:
Ég skil þetta = I understand this

It is in the accusative/neuter singular form, which is what you expect here because:

• skilja takes a direct object
• the thing being understood is þetta

This is a very common form learners see early on.

It literally means this, but in real usage it can refer to something already understood from context.

So Ég skil þetta could mean:

• I understand this
• I understand it
• I understand what you’re saying

The exact English wording depends on the situation, even though the Icelandic stays the same.

Auðveldlega is an adverb, meaning easily.

It describes how the understanding happens:

• Ég skil þetta = I understand this
• Ég skil þetta auðveldlega = I understand this easily

A lot of Icelandic adverbs are formed with -lega, similar to English -ly:

• auðveldur = easy
• auðveldlega = easily

Yes, adverb placement can vary somewhat in Icelandic, but this position is very natural:

• Ég skil þetta auðveldlega þegar þú talar hægt.

Here, auðveldlega comes after the object þetta and before the subordinate clause þegar þú talar hægt.

Other placements may be possible depending on emphasis, but for a learner this version is a good, natural model to follow.

Here þegar means when.

It introduces a time clause:

• þegar þú talar hægt = when you speak slowly

So the sentence structure is:

• main clause: Ég skil þetta auðveldlega
• time clause: þegar þú talar hægt

In other contexts, þegar can also mean when in the sense of a specific time or situation.

Because þegar þú talar hægt is a subordinate clause, and this word order is normal.

• þú = you
• talar = speak
• hægt = slowly

So the clause is simply:

• þegar þú talar hægt = when you speak slowly

Learners sometimes expect unusual word order after words like when, but this is a straightforward and common pattern.

Talar is the 2nd person singular present form of tala, which means to speak.

So:

• að tala = to speak
• þú talar = you speak

That is why the sentence says þú talar hægt = you speak slowly.

Yes, it comes from the adjective hægur = slow.

In Icelandic, the neuter singular form of an adjective is often used adverbially, especially for simple adverbs of manner.

So:

• hægur = slow (masculine adjective form)
• hægt = slow in neuter form, but also slowly as an adverb

That is why:

• tala hægt = to speak slowly

This is a very common Icelandic pattern.

Usually, no—not in this sentence.

Even though many Icelandic adverbs end in -lega, hægt is the normal word for slowly here:

• þú talar hægt = you speak slowly

So this is something learners should treat as the standard expression.

Ég means I.

The accent mark shows that the vowel is pronounced differently from plain e. Icelandic accents are not optional spelling marks; they are part of the word.

A rough guide:

• Ég is pronounced approximately like yeg or yeh-g, depending on accent and speech
• the g is not always pronounced the way English speakers expect

The important thing for learners is to recognize Ég instantly as the subject pronoun I.

This sentence contains þ in þetta and þú.

• þ is called thorn
• it usually sounds like the th in thing

So:

• þetta
• þú

both begin with that kind of th sound.

There is no ð in this sentence, but learners often ask about it because Icelandic uses both letters:

• þ ≈ th in thing
• ð ≈ th in this

That is a useful starting point, even though the real pronunciation can be more nuanced.

It can very naturally mean a general situation or repeated pattern:

• I understand this easily when you speak slowly

That sounds like something that is generally true, not just true once.

The present tense in Icelandic often works like this, just as in English.

Yes.

• Ég skil þetta þegar þú talar hægt.
  = I understand this when you speak slowly.

That is still completely correct.

Adding auðveldlega simply adds the idea of easily:

• Ég skil þetta auðveldlega þegar þú talar hægt.

So the adverb gives extra information, but it is not required for the grammar to work.