De organiserer en protest.

Here, De is most naturally understood as they.

A useful thing to know is that De with a capital D can also be an old-fashioned or very formal way to say you in Norwegian. However:

• in modern everyday Norwegian, that formal De is rare
• at the beginning of a sentence, de is capitalized anyway, so De does not automatically mean formal you

So in a normal learning context, De organiserer en protest is understood as They are organizing a protest / They organize a protest, depending on context.

Organiserer is the present tense of the verb å organisere (to organize).

So:

• å organisere = to organize
• organiserer = organize / is organizing / are organizing

In Norwegian, the present tense often covers both the simple present and the present progressive that English separates:

• De organiserer en protest = They organize a protest or They are organizing a protest

Context usually tells you which one is meant.

No. Norwegian verbs do not change for person the way English verbs do.

In English, you get:

• I organize
• she organizes
• they organize

In Norwegian, the present tense stays the same:

• jeg organiserer
• du organiserer
• han/hun organiserer
• vi organiserer
• de organiserer

So organiserer is used with all subjects in the present tense.

En protest means a protest.

• protest is a noun
• en is the indefinite article for many Norwegian nouns, similar to English a

So:

• en protest = a protest
• protesten = the protest

The noun protest is a common-gender noun in Bokmål, so it takes en.

Usually, no—not in this sentence if you mean a protest as a countable event.

In Norwegian, as in English, singular countable nouns usually need an article:

• De organiserer en protest = correct
• De organiserer protest = usually not natural for this meaning

You might omit an article in some fixed expressions or more abstract uses, but for a normal sentence about one protest, en is the expected form.

The basic word order is:

Subject + Verb + Object

So here:

• De = subject
• organiserer = verb
• en protest = object

This is the normal main-clause word order in Norwegian, just like in a simple English sentence such as They organize a protest.

This is Bokmål.

In Nynorsk, you would more likely see:

• Dei organiserer ein protest

Compare:

• Bokmål: De organiserer en protest
• Nynorsk: Dei organiserer ein protest

So if you are studying standard written Norwegian, this sentence is in Bokmål.

A rough pronunciation guide for an English speaker:

• De ≈ deh
• organiserer ≈ or-ga-ni-SE-rer
• en protest ≈ en pro-TEST

A few notes:

• the r sound in Norwegian is usually clearer than in many English accents
• the stress in protest is normally on the last syllable in Norwegian: pro-TEST
• organiserer has a rhythm a bit like or-ga-ni-SE-rer

Pronunciation varies somewhat by dialect, but that stress pattern is a good starting point.

It can mean either, depending on context.

Norwegian present tense is flexible, so this sentence could mean:

• They are organizing a protest right now / these days
• They organize a protest as a habitual or scheduled action

If you want to make the ongoing sense clearer, context usually does the job. Norwegian often does not need a separate form like English are organizing.

No. Organisere is a very natural choice, but other verbs are also possible depending on nuance.

For example:

• De arrangerer en protest = They are arranging a protest
• De planlegger en protest = They are planning a protest
• De setter i gang en protest = They are starting/launching a protest

But De organiserer en protest is completely correct and idiomatic if the idea is that they are organizing the event.

Because en protest means one protest.

If you wanted protests in the plural, you would say:

• protester = protests

So:

• De organiserer en protest = They are organizing a protest
• De organiserer protester = They are organizing protests

The sentence you were given is singular, so en protest is the right form.