Það gleður mig að þú viljir læra meira íslensku.

Here það is a dummy subject, much like English it in It makes me happy that...

The real content is in the clause að þú viljir læra meira íslensku, but Icelandic often puts that heavier clause later and uses það in the subject position first.

So structurally, this is very similar to:

• It pleases me that...
• Það gleður mig að...

You can also say Að þú viljir læra meira íslensku gleður mig, but that sounds more formal or literary.

Because the verb gleðja takes a direct object in the accusative.

So:

• gleðja einhvern = to make someone glad
• mig = me in the accusative

That means mig is correct here.

This is one of those things you simply learn with the verb:

• Það gleður mig = it gladdens me / it makes me happy

A learner may expect mér because many Icelandic feeling-expressions use the dative, but gleðja is not one of them.

Gleður is the 3rd person singular present tense of gleðja.

Why 3rd person singular?

Because the grammatical subject is það, and það is singular.

So:

• að gleðja = to gladden / make glad
• það gleður = it gladdens

Here að means that and introduces a subordinate clause:

• að þú viljir læra meira íslensku = that you want to learn more Icelandic

This is different from the other common use of að, where it can mark an infinitive, similar to English to.

So in this sentence, að is a conjunction, not an infinitive marker.

Viljir is the present subjunctive form of vilja.

• indicative: þú vilt = you want
• subjunctive: þú viljir

Icelandic often uses the subjunctive in subordinate clauses after expressions involving attitude, feeling, evaluation, or non-neutral perspective. In a sentence like Það gleður mig að..., the speaker is reacting emotionally to the content of the clause, and that often triggers the subjunctive.

So að þú viljir... is a very natural, grammatically careful way to say it.

Not always in every context of everyday speech, but learners should recognize that viljir is the expected textbook-style form here and is fully natural.

The important point is:

• vilt = indicative
• viljir = subjunctive

In this sentence, the subjunctive shows the kind of clause Icelandic often uses after expressions like það gleður mig að...

So even if you later hear some variation in informal speech, viljir is the form worth learning here.

Because vilja is followed by a bare infinitive in Icelandic.

So you say:

• vilja læra = want to learn
• vilja fara = want to go
• vilja skilja = want to understand

English uses to after want, but Icelandic does not use að there with vilja.

So:

• þú viljir læra = that you want to learn

not

• þú viljir að læra

In this sentence, meira means more, and the phrase læra meira íslensku means learn more Icelandic.

A useful way to understand it is:

• læra meira = learn more
• íslensku = Icelandic

So meira is functioning very naturally with the whole verbal idea, not just as a simple agreeing adjective directly attached to íslensku.

For a learner, the safest thing is to treat læra meira íslensku as a common, idiomatic pattern.

Íslensku here is the accusative singular of íslenska, meaning the Icelandic language.

Why accusative?

Because it is the object of læra:

• læra íslensku = learn Icelandic

So the base dictionary form is:

• íslenska

and in this sentence you get:

• íslensku

It is a noun here.

Even though English uses Icelandic both as an adjective and as a noun, Icelandic uses íslenska as a noun meaning the Icelandic language.

So in this sentence:

• íslensku does not mean Icelandic as an adjective before another noun
• it means the Icelandic language

That is why it can stand as the object of læra all by itself.

Because this is a subordinate clause, and Icelandic word order is different there from main-clause word order.

In main clauses, Icelandic often follows a verb-second pattern. But after að, the normal order is:

• subject + finite verb

So:

• að þú viljir = correct

not:

• að viljir þú

That subject-before-verb order is what learners should expect in most að-clauses.

Yes. That is grammatically correct.

It puts the that-clause first, so the sentence feels a bit more formal, weighty, or literary:

• Að þú viljir læra meira íslensku gleður mig.

The version with það is more conversational and more typical in everyday use:

• Það gleður mig að þú viljir læra meira íslensku.

Both are correct; the difference is mostly one of style and sentence flow.