Hún skrifar með merkipennanum og tekur borðið í sundur.

Yes, hún usually means she.

In Icelandic, personal pronouns are inflected for case, but here hún is the subject of the sentence, so it is in the nominative case.

A few useful forms are:

• hún = she (nominative)
• hana = her (accusative)
• henni = her (dative)
• hennar = her / hers (genitive)

So in Hún skrifar..., hún is the person doing the actions: writing and taking the table apart.

Skrifar is the present tense form of the verb að skrifa = to write.

So:

• að skrifa = to write
• ég skrifa = I write
• hún skrifar = she writes

In Icelandic, verbs change depending on the subject, and -ar is a very common present-tense ending with he/she/it for many verbs.

So:

• Hún skrifar = She writes

Because the preposition með usually takes the dative case when it means with in the sense of using something.

The dictionary form is:

• merkipenni = marker, felt-tip pen

But after með, it changes to the dative:

• með merkipenna = with a marker

And because this sentence says with the marker, Icelandic adds the definite article onto the noun:

• merkipennanum = the marker in the dative singular

So:

• með merkipennanum = with the marker

This is one of the most important things to learn in Icelandic: prepositions often control a specific case.

Because Icelandic usually puts the at the end of the noun instead of using a separate word like English does.

So:

• merkipenni = a marker
• merkipenninn = the marker
• merkipennanum = to/with the marker, depending on context and case

And:

• borð = table
• borðið = the table

This is called the suffixed definite article. It is extremely common in Icelandic.

So in this sentence, both merkipennanum and borðið already include the meaning of the.

Borðið comes from borð = table.

Here it means the table.

This noun is neuter, and the definite nominative/accusative singular form is:

• borðið = the table

In this sentence, borðið is the direct object of tekur:

• tekur borðið í sundur = takes the table apart

For many neuter nouns in Icelandic, the nominative and accusative forms are the same, so even though it is the object, it still appears as borðið.

Tekur is the present tense of að taka = to take.

So:

• að taka = to take
• hún tekur = she takes

But in this sentence, it is part of the expression:

• taka ... í sundur = take ... apart

So the meaning is not just plain take. It is the phrasal-style expression take apart / dismantle.

Í sundur means apart, to pieces, or into pieces, depending on context.

In this sentence:

• tekur borðið í sundur = takes the table apart

This is a very common Icelandic expression:

• að taka eitthvað í sundur = to take something apart
• að fara í sundur = to come apart, break apart
• að rífa eitthvað í sundur = to tear something apart

So you should learn í sundur as a useful expression meaning physical separation into parts.

Yes. It is best to learn að taka eitthvað í sundur as a whole pattern.

The structure is:

• taka + object + í sundur

Examples:

• Hún tekur borðið í sundur. = She takes the table apart.
• Ég tók tölvuna í sundur. = I took the computer apart.
• Þeir tóku leikfangið í sundur. = They took the toy apart.

So although taka by itself means take, when combined with í sundur it gets the more specific meaning take apart / dismantle.

Because that is the normal and very natural Icelandic word order for this expression:

• taka borðið í sundur

The object often goes between the verb and the particle/expression, much like English:

• take the table apart

That said, Icelandic word order can sometimes vary for emphasis or style, but for learners, verb + object + í sundur is the safest pattern to remember.

Mostly yes. Og simply means and.

Here it connects two verbs with the same subject:

• Hún skrifar ... og tekur ...
• She writes ... and takes ...

Since the subject hún already appears at the start, Icelandic does not need to repeat it before the second verb.

So the sentence structure is basically:

• She writes with the marker and takes the table apart.

Yes. The sentence has one subject, hún, and two coordinated actions:

1. skrifar með merkipennanum = writes with the marker
2. tekur borðið í sundur = takes the table apart

The conjunction og joins them.

This is very common in Icelandic and works much like English:

• She writes with the marker and takes the table apart.

So grammatically, one person is doing both actions.