Við notum rúlluna þegar við viljum mála hraðar og betur.

Við means we.

It appears twice because the sentence has two clauses:

• Við notum rúlluna = We use the roller
• þegar við viljum mála hraðar og betur = when we want to paint faster and better

So Icelandic, like English, normally repeats the subject in each clause instead of leaving it out.

Notum means use in we use.

Its dictionary form is nota = to use.

Here is the pattern:

• að nota = to use
• ég nota = I use
• við notum = we use

So -um is the present-tense ending here for we.

Rúlluna means the roller, while rúlla means just roller.

Icelandic usually adds the definite article to the end of the noun rather than using a separate word like the.

So:

• rúlla = a roller / roller
• rúllan = the roller
• rúlluna = the roller (object form)

In this sentence, the roller is the thing being used, so it appears in the accusative case.

The dictionary form is rúlla.

More specifically:

• rúlla = roller
• rúllan = the roller
• rúlluna = the roller (accusative singular)

If the meaning shown to the learner is about painting, then this most likely refers to a paint roller.

The ending comes from two things combined:

• the noun changes form for case
• the definite article is attached to the end

For this feminine noun:

• rúlla = nominative indefinite
• rúlluna = accusative definite

Since nota takes a direct object, and the roller is that object, Icelandic uses the accusative form rúlluna.

Þegar means when here.

It introduces a time clause:

• þegar við viljum mála hraðar og betur
• when we want to paint faster and better

So the full sentence means that we use the roller when we want to paint faster and better.

Viljum means want in we want.

Its dictionary form is vilja = to want.

So:

• að vilja = to want
• við viljum = we want

This is an important common verb in Icelandic.

After vilja (to want), Icelandic normally uses the infinitive directly, without að.

So you say:

• við viljum mála = we want to paint

Not:

• við viljum að mála

This is similar to English, where we say want to paint, but the Icelandic structure does not use að in this pattern.

Mála means to paint.

Its dictionary form is also mála, because infinitives in Icelandic often end in -a.

So in the sentence:

• við viljum mála = we want to paint

Because they are modifying the verb mála (to paint), not a noun.

That means Icelandic uses adverbs, not adjectives:

• hraðar = faster
• betur = better

Compare:

• hraðari bíll = a faster car → adjective, describing a noun
• mála hraðar = paint faster → adverb, describing how the action is done

And:

• betri pensill = a better brush → adjective
• mála betur = paint better → adverb

Yes. Betur is the comparative adverb of vel (well).

So:

• vel = well
• betur = better

This is similar to English, where well becomes better, not more well.

Yes. Hraðar means faster and is the comparative adverb related to hratt (quickly / fast).

So:

• hratt = quickly, fast
• hraðar = faster

In this sentence, hraðar og betur means faster and better.

It has a very clear two-part structure:

• Við notum rúlluna
  main clause: We use the roller
• þegar við viljum mála hraðar og betur
  subordinate clause: when we want to paint faster and better

A word-for-word breakdown is:

• Við = we
• notum = use
• rúlluna = the roller
• þegar = when
• við = we
• viljum = want
• mála = paint
• hraðar = faster
• og = and
• betur = better

Yes. You can put the þegar clause first:

• Þegar við viljum mála hraðar og betur, notum við rúlluna.

This still means the same thing: When we want to paint faster and better, we use the roller.

Notice what happens in the main clause after the fronted clause:

• notum við
  not við notum

That is because Icelandic often follows verb-second word order in main clauses.

A few words may stand out to an English speaker:

• við: the ð is like the th in this
• þegar: the þ is like the th in thin
• viljum: the lj combination can be tricky for learners
• rúlluna: the ú is a long vowel, roughly like oo but not exactly the same as English

Even if pronunciation is difficult at first, the most important thing for understanding this sentence is recognizing the grammar and word forms.