Þegar það er hálka á veginum, reyni ég að bremsa mjög varlega.

Hálka means slippery conditions caused by ice, especially on roads or sidewalks. It is often translated as ice or icy/slippery conditions, depending on context.

So in það er hálka á veginum, the idea is not just there is ice, but more specifically the road is slippery because of ice.

Here það works like it/there in English weather and condition expressions.

So:

• það er kalt = it is cold
• það er rok = it is windy
• það er hálka = there is ice / it is icy

Even though það usually means it/that, in sentences like this it is often just part of the standard way to express a condition.

Because the preposition á can take different cases depending on meaning.

Here it means on the road in a static location sense, so it takes the dative:

• vegur = road
• dative singular = vegi
• with the definite article = veginum = the road

So:

• á veginum = on the road

A useful rule:

• á + dative = location, being on something
• á + accusative = movement onto something

Examples:

• Bíllinn er á veginum. = The car is on the road.
• Bíllinn fer á veginn. = The car goes onto the road.

This is a very common Icelandic pattern. After a clause like Þegar það er hálka á veginum (When there is ice on the road), the main clause usually has verb-second word order.

That means the finite verb comes first in the main clause after the opening clause:

• Þegar það er hálka á veginum, reyni ég að bremsa mjög varlega.

Literally, the structure is:

• When ... , try I ...

This is normal Icelandic grammar, not poetic or unusual.

Compare:

• Ég reyni að bremsa mjög varlega þegar það er hálka á veginum.
  • Here the sentence starts with Ég, so normal subject + verb order appears.

But if the when-clause comes first, then the main clause flips:

• Þegar ..., reyni ég ...

Reyni is from the verb að reyna, meaning to try.

When one verb is followed by another infinitive, Icelandic often uses að before the second verb:

• að reyna að bremsa = to try to brake

So:

• reyni ég að bremsa = I try to brake

This is similar to English try to do something.

Examples:

• Ég reyni að sofa. = I try to sleep.
• Hún reynir að læra íslensku. = She tries to learn Icelandic.

Because reyni is the 1st person singular present tense form of að reyna.

So:

• að reyna = to try (infinitive)
• ég reyni = I try

A few present-tense forms:

• ég reyni = I try
• þú reynir = you try
• hann/hún/það reynir = he/she/it tries
• við reynum = we try

So in the sentence, reyni ég simply means I try, with the verb moved before the subject because of word order.

Að bremsa means to brake.

Yes, it is a normal and common Icelandic verb, especially in everyday speech about driving. It is related to bremsa meaning brake.

So:

• að bremsa = to brake
• ég bremsa = I brake

In your sentence:

• að bremsa mjög varlega = to brake very gently/carefully

Varlega means carefully, gently, or cautiously.

In this sentence, because it is talking about braking on an icy road, very gently is often the most natural sense:

• mjög varlega = very carefully / very gently

That is exactly what you do on ice: you brake softly and cautiously.

Related word:

• varlegur / varleg / varlegt = careful, cautious
• varlega = carefully, cautiously

Because mjög is the normal word for very before adjectives and adverbs.

• mjög varlega = very carefully
• mjög kalt = very cold
• mjög góður = very good

Mikið usually means much / a lot, and it is used differently.

So a good rule is:

• mjög = very
• mikið = much/a lot

Yes, that is possible.

• Þegar það er hálka á veginum
• Þegar hálka er á veginum

Both are understandable and grammatical. The version with það er often sounds a bit more natural and everyday, because Icelandic frequently uses this kind of expression for weather and road conditions.

So for a learner, það er hálka is a very useful pattern to remember.

On the road is the correct translation here.

Icelandic á often means on, and with roads the natural English choice is also on:

• á veginum = on the road

English in the road usually suggests something physically located in the roadway, like:

• There is a rock in the road.

But here the meaning is that the road surface itself is icy, so on the road is the natural translation.

Here are some rough pronunciation guides for English speakers:

• Þegar ≈ THYE-ghar
  
  • Þ is like th in thin
• það ≈ thath
  
  • again th as in thin
• hálka ≈ HOWL-ka
• veginum ≈ VEH-yi-num or VEH-gi-num depending on speech style
• reyni ≈ RAY-ni
• bremsa ≈ BREYM-sa
• varlega ≈ VAR-leh-ga

These are only approximate. Icelandic pronunciation varies a little by speaker, but the hardest sounds for English speakers here are usually þ and the vowel combinations.

It breaks down like this:

• Þegar = when
• það er hálka = there is ice / it is icy
• á veginum = on the road
• reyni ég = I try
• að bremsa = to brake
• mjög varlega = very carefully / very gently

So the full structure is:

When there are icy conditions on the road, I try to brake very carefully.

This sentence is a good example of:

1. a subordinate time clause with þegar
2. normal Icelandic verb-second order in the main clause
3. an infinitive construction with að reyna að...