Þetta er raunverulegt vandamál.

It breaks down like this:

• Þetta = this
• er = is
• raunverulegt vandamál = a real problem

So the pattern is:

• subject
  • verb
    • predicate noun phrase

This is very similar to English This is a real problem.

Þetta is the neuter singular form of the demonstrative this.

It is used here as a stand-alone pronoun, not directly before a noun. So it means something like:

• this
• this thing
• this situation

Icelandic often uses neuter singular for general or abstract this, especially when referring to a whole situation rather than naming a specific masculine or feminine noun.

It also fits well here because vandamál is a neuter noun.

Er is the present tense, 3rd person singular form of vera, which means to be.

So:

• ég er = I am
• þú ert = you are
• þetta er = this is

Because þetta is grammatically singular, the verb is singular too: er.

Because it has to agree with vandamál.

In Icelandic, adjectives change form to match the noun in:

• gender
• number
• case
• and often definiteness

Here, vandamál is:

• neuter
• singular
• nominative

So the adjective raunverulegur becomes raunverulegt.

A useful comparison:

• raunverulegur = masculine
• raunveruleg = feminine
• raunverulegt = neuter

Since vandamál is neuter, raunverulegt is the correct form.

It is in the nominative.

After vera (to be), Icelandic normally uses a predicate nominative, not an accusative object. So in a sentence like this, both sides are nominative in meaning and structure:

• Þetta = nominative subject
• raunverulegt vandamál = nominative complement

That is why you should not think of vandamál as a direct object here.

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

So:

• raunverulegt vandamál = a real problem

If you want the problem, Icelandic usually uses a suffixed definite article on the noun:

• vandamál = a problem / problem
• vandamálið = the problem

So the sentence is indefinite simply because the noun appears without the definite ending.

That is the normal position in Icelandic.

So:

• raunverulegt vandamál = real problem

Like English, Icelandic usually puts attributive adjectives before the noun.

If the adjective comes after the noun, that is usually not the normal plain pattern and may suggest a different structure or a more marked style.

Yes, but it means something slightly different.

• Þetta er raunverulegt vandamál = This is a real problem
• Þetta vandamál er raunverulegt = This problem is real

In the original sentence, þetta refers to a situation or thing, and you identify it as a real problem.

In Þetta vandamál er raunverulegt, the subject is specifically this problem, and the sentence says that the problem is real.

So both are correct, but the focus changes.

Because raunverulegt is an adjective, while raunverulega is usually an adverb or a weak adjective form in other contexts.

Here you need an adjective modifying vandamál, so it must agree with the noun:

• raunverulegt vandamál = a real problem

If you said raunverulega here, it would sound wrong in this structure.

A helpful contrast:

• raunverulegt vandamál = a real problem
• raunverulega = really / genuinely in many contexts as an adverb

Here it is singular and means problem.

It is a neuter noun, and it can look unusual because some Icelandic neuter nouns have the same form in more than one case, and sometimes even the same nominative/accusative form in singular and plural.

For a learner, the important thing here is:

• vandamál = problem
• it is neuter
• in this sentence it is singular nominative

So the adjective must be neuter singular too: raunverulegt.

A rough learner-friendly guide:

• Þ in Þetta is like th in thing
• stress usually falls on the first syllable of each word
• au in raun- is roughly like oy in boy
• á in vandamál is roughly like ow in now

So a very rough approximation is:

THETH-ta er ROYN-veru-lekht VAN-da-maul

A few notes:

• Icelandic pronunciation is not exactly captured by English spelling
• the tt in þetta has a special Icelandic sound
• the ending -gt in raunverulegt is not pronounced like plain English gt

So this kind of approximation is useful at first, but listening to native audio is very important.

Yes. It is a very normal basic statement:

• Þetta = subject
• er = verb
• raunverulegt vandamál = complement

So the order is straightforward and very natural.

More generally, Icelandic is often described as a verb-second language in main clauses, but in a simple sentence like this, the word order looks very much like English.