Ég skil betur það sem kennarinn skrifar á töfluna þegar framburðurinn er skýr.

Það sem means what or that which.

So:

• það sem kennarinn skrifar = what the teacher writes

This is a very common Icelandic structure called a free relative. English usually just says what, but Icelandic often uses það sem.

You usually cannot translate it word-for-word in a natural way. It is best to learn it as one unit:

• það sem = what

Because sem by itself usually introduces a clause that refers back to a noun already mentioned:

• bókin sem ég les = the book that I am reading

But in your sentence, there is no earlier noun like the thing or the text. The clause itself is the object of skil. So Icelandic uses það sem:

• Ég skil það sem kennarinn skrifar = I understand what the teacher writes

If you remove það, the sentence sounds incomplete or ungrammatical in standard Icelandic.

Betur means better. It is the comparative form of vel (well).

• vel = well
• betur = better
• best = best

So:

• Ég skil vel = I understand well
• Ég skil betur = I understand better

This is like English well → better, not well → more well.

Because skilja is the infinitive: to understand.

In the sentence, you need the present tense for I understand:

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

So Ég skil betur... means I understand better...

Kennarinn means the teacher, while kennari means a teacher or just teacher.

Icelandic usually adds the definite article to the end of the noun:

• kennari = teacher
• kennarinn = the teacher

So:

• það sem kennarinn skrifar = what the teacher writes

The sentence is talking about a specific teacher, not just any teacher.

Skrifar is the present tense of skrifa (to write) for he/she/it.

• að skrifa = to write
• ég skrifa = I write
• þú skrifar = you write
• hann/hún/það skrifar = he/she/it writes

Since kennarinn (the teacher) is third-person singular, the verb is:

• kennarinn skrifar = the teacher writes

This is a very common Icelandic case pattern with prepositions.

With á:

• accusative often suggests movement toward something or an action directed onto a surface
• dative often suggests location on something

Here, skrifa á töfluna means writing onto the board / on the board as a target surface.

Compare:

• skrifa á töfluna = write on the board / onto the board
• eitthvað er á töflunni = something is on the board

So á töfluna is natural because the writing is being put onto the board.

Töfluna is accusative singular definite of tafla (board, table, depending on context).

Basic forms:

• tafla = a board
• töfluna = the board (accusative)
• töflunni = the board (dative)

In this sentence, á takes the accusative because of the idea of writing onto the board.

You may also notice the stem changes a little:

• tafla
• töflu-

That kind of vowel change is common in Icelandic noun inflection.

Framburðurinn means the pronunciation.

Icelandic often uses the definite form where English might be a little more flexible. Here it refers to the specific pronunciation involved in the situation—the pronunciation being heard.

So:

• framburður = pronunciation
• framburðurinn = the pronunciation

Using the definite form makes it sound more specific and natural in context.

Because skýr has to agree with framburðurinn.

Framburður is a masculine noun, singular, and here it is nominative. So the adjective must match:

• masculine singular: skýr
• neuter singular: skýrt
• feminine singular: skýr

So:

• framburðurinn er skýr = the pronunciation is clear

If the noun were neuter, then skýrt would be correct.

After þegar (when), Icelandic uses normal subordinate-clause word order:

• þegar framburðurinn er skýr

That means:

• þegar = when
• framburðurinn = the pronunciation
• er = is
• skýr = clear

You do not put the verb first there.

A useful comparison:

• Ég skil betur ... þegar framburðurinn er skýr.
• Þegar framburðurinn er skýr, skil ég betur ...

In the second version, because the þegar clause comes first, the main clause shows the usual Icelandic inversion:

• skil ég not
• ég skil

It can be understood as either when or whenever, depending on context.

In a sentence like this, it often has a general meaning:

• I understand better when/whenever the pronunciation is clear

So even though þegar literally means when, in practice it can describe a repeated or general situation.

Not quite.

A very literal breakdown is:

• Ég = I
• skil betur = understand better
• það sem = what / that which
• kennarinn skrifar = the teacher writes
• á töfluna = on/onto the board
• þegar framburðurinn er skýr = when the pronunciation is clear

So the sentence is quite close to English overall, but two things are especially Icelandic:

1. það sem for what
2. the case choice in á töfluna

Those are good patterns to remember because they come up often.