Ég rata betur þegar ég er með kort.

Because betur is the comparative adverb meaning better.

In this sentence, it modifies the verb rata (to find one’s way / navigate), so Icelandic uses an adverb, not an adjective.

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

By contrast, betra is usually the neuter form of the adjective betri (better) and would be used to describe a noun, not to modify a verb.

So:

• Ég rata betur = I find my way better
• not Ég rata betra

Rata is a very common Icelandic verb meaning something like:

• to find one’s way
• to know the way
• to manage to navigate

It is often used where English might use several different expressions, such as:

• I can find my way
• I know where I’m going
• I don’t get lost
• I can navigate

So Ég rata betur does not literally mean just I better, but more naturally I find my way better or I navigate better.

Because Icelandic, like English, normally repeats the subject in a new clause.

The sentence has two clauses:

1. Ég rata betur = I find my way better
2. þegar ég er með kort = when I have a map

The second clause needs its own subject, so Icelandic says þegar ég er..., just as English says when I am....

Here, þegar means when.

It introduces a time clause:

• þegar ég er með kort = when I have a map

Be aware that þegar can also mean already in other contexts, so learners often notice it has more than one use.

For example:

• Ég er þegar kominn = I have already arrived
• Þegar ég er með kort... = When I have a map...

So the meaning depends on how it is used in the sentence.

Because after a subordinating conjunction like þegar (when), Icelandic usually has normal subordinate-clause word order:

• þegar ég er með kort

That means:

1. conjunction
2. subject
3. verb

This is similar to English: when I am...

Learners often hear that Icelandic is a verb-second language, and that is true in many main clauses. But subordinate clauses like this one do not usually keep that same main-clause pattern.

Yes, með usually means with, but vera með is also a very common everyday expression meaning:

• to have
• to be carrying
• to have with you
• to be using

So ég er með kort is naturally understood as:

• I have a map
• I’ve got a map
• I’m carrying a map

In this sentence, the sense is basically having a map available.

This is a very good question, because learners often expect með to take the dative.

Normally, the preposition með does go with the dative when it means with in the usual prepositional sense.

However, in the common expression vera með e-ð (to have something / be carrying something), the noun is often treated as the object of the whole expression, and you get the accusative.

So here:

• kort = accusative singular of kort
• ég er með kort = I have a map

That is why you do not see korti here.

Because Icelandic does not have an indefinite article like English a/an.

So a bare noun can mean:

• a map
• map (depending on context)

Here kort means a map.

Compare:

• ég er með kort = I have a map
• ég er með kortið = I have the map

The ending -ið is the definite article attached to the noun.

Because the sentence is describing a general situation or habitual truth:

• I find my way better when I have a map

English also uses the present tense here. Icelandic does the same.

So þegar ég er með kort does not mean only right now when I am with a map, but more generally whenever I have a map.

Yes, but the meaning changes slightly.

• þegar ég er með kort = when I have a map
• ef ég er með kort = if I have a map

Using þegar suggests that this is something that happens at those times when the condition is true.

Using ef makes it sound more conditional or hypothetical.

So:

• Ég rata betur þegar ég er með kort.
  = I find my way better when I have a map.

• Ég rata betur ef ég er með kort.
  = I find my way better if I have a map.

Both are possible, but þegar sounds more like a general repeated situation.

Yes.

Ég rata betur is already a complete sentence meaning:

• I find my way better
• I navigate better

The þegar clause simply adds more information about when that is true:

• Ég rata betur
• þegar ég er með kort

So the second part is optional extra information, not something required by the verb.

Yes. That is exactly what happens here.

You can use rata in a general sense, meaning that someone can find their way around, without stating a destination.

But you can also be more specific, for example:

• Ég rata heim. = I can find my way home.
• Ég rata í skólann. = I can find my way to the school.

In your sentence, the meaning is general: I’m better at finding my way.

Yes.

• Ég rata vel... = I find my way well...
• Ég rata betur... = I find my way better...

The difference is that betur is comparative. It implies comparison, even if the comparison is not stated explicitly.

So Ég rata betur þegar ég er með kort suggests:

• better than when I do not have a map
• better than usual
• better under those circumstances

That is why betur is especially natural here.