Ruslatunnan er full, svo ég tek ruslið út núna.

Because Icelandic usually writes compound nouns as a single word.

So ruslatunnan is one compound noun meaning the trash can / the garbage bin.
English often splits similar ideas into two words, but Icelandic very often joins them:

• ruslatunna = trash can / garbage bin
• baðherbergi = bathroom
• eldhús = kitchen

This is one of the first things English speakers have to get used to in Icelandic.

In Icelandic, the definite article is usually attached to the end of the noun instead of being a separate word.

So:

• ruslatunna = a trash can
• ruslatunnan = the trash can

and

• rusl = trash / garbage
• ruslið = the trash / the garbage

That means Icelandic often expresses the as a suffix rather than as a separate word like English does.

• ruslatunnan is in the nominative because it is the subject of er full.
• ruslið is in the accusative because it is the direct object of tek.

So the structure is:

• Ruslatunnan = the trash can, as the thing being described
• ég tek ruslið út = I take the trash out, where ruslið is the thing being taken out

A useful point here is that ruslið looks the same in nominative and accusative, which is common for many neuter nouns in Icelandic.

Because the adjective has to agree with ruslatunnan.

Ruslatunnan is:

• singular
• feminine
• nominative

So the adjective must also be feminine singular nominative:

• masculine: fullur
• feminine: full
• neuter: fullt

That is why the sentence says:

• Ruslatunnan er full

If the noun were neuter, you would get fullt instead.

Because tek is the present-tense form of the verb taka for ég.

The verb is taka = to take, but verbs change form depending on the subject and tense.

Here:

• að taka = to take
• ég tek = I take / I am taking

So ég tek ruslið út núna means I’m taking the trash out now or I take the trash out now, depending on context.

This is also an irregular verb, so the stem changes:

• taka
• tek

Because út is acting like a particle here, similar to out in English take the trash out.

In Icelandic main clauses, this particle often comes after the object:

• ég tek ruslið út

That word order is very natural.
It works much like English:

• take out the trash
• take the trash out

Icelandic often prefers the pattern verb + object + particle in a simple sentence like this.

Here svo means so / therefore, and it is functioning as a conjunction linking two clauses:

• Ruslatunnan er full
• svo ég tek ruslið út núna

After this kind of conjunction, Icelandic can keep normal subject-verb order:

• svo ég tek...

An English speaker may expect inversion because Icelandic often has verb-second word order, but conjunctions like og, en, and svo do not automatically force inversion in this kind of sentence.

So svo ég tek ruslið út núna is perfectly normal.

Because Icelandic, like English, often uses the present tense for an immediate or very near future action.

So:

• ég tek ruslið út núna

can mean:

• I’m taking the trash out now
• I’ll take the trash out now

The word núna makes it clear that this is happening immediately, so the plain present tense sounds natural.

They are related, but they do not mean the same thing:

• ruslatunna = trash can / garbage bin
• rusl = trash / garbage / rubbish

So in the sentence:

• Ruslatunnan er full = the container is full
• ég tek ruslið út = I take the garbage out

English also makes this distinction, but Icelandic uses two clearly different nouns.

Because time words are often placed later in the sentence in Icelandic, especially when they modify the whole action.

So:

• ég tek ruslið út núna

is a very natural way to say I’m taking the trash out now.

You could move núna for emphasis, but the meaning or tone would shift a little. For example:

• Núna tek ég ruslið út = emphasizes now
• Ég tek ruslið út núna = more neutral, everyday wording

So the position in your sentence is natural and common.

Because the sentence contains two clauses:

• Ruslatunnan er full
• svo ég tek ruslið út núna

The comma helps separate them, just as English often does before so when it joins two full clauses.

So the punctuation reflects the structure:

1. the trash can is full
2. therefore I’m taking the trash out now

It makes the sentence easier to read and shows the logical connection between the two parts.