Hann ætlar að láta snyrta skeggið sitt á morgun.

Ætlar að means intends to, is planning to, or often simply is going to.

So Hann ætlar að... means He is going to... or He plans to...

It is a very common way to talk about future plans in Icelandic.

Here láta is being used in a causative sense. That means the subject causes something to happen, rather than doing it personally.

So:

• láta snyrta skeggið sitt = have his beard trimmed
• literally, it is something like cause/arrange for the beard to be trimmed

This is similar to English expressions like:

• He is going to have his beard trimmed tomorrow
• He is going to get his beard trimmed tomorrow

It strongly suggests that someone else will do the trimming.

Snyrta is the infinitive form of the verb, meaning to trim / to tidy up / to groom.

After láta in this kind of construction, Icelandic commonly uses the infinitive:

• láta gera = have something done
• láta laga = have something fixed
• láta snyrta = have something trimmed

So láta snyrta skeggið sitt follows a very normal pattern.

In this sentence, snyrta means something like:

• trim
• tidy up
• groom

Because the object is skeggið sitt (his beard), the most natural English meaning is trim his beard or groom his beard.

It does not necessarily mean shaving it off completely. It usually suggests making it neat.

Skegg means beard.
Skeggið means the beard.

Icelandic usually adds the definite article to the end of the noun, instead of putting a separate word in front like English the.

So:

• skegg = beard
• skeggið = the beard

That is why you see the ending -ið attached to the noun.

Sitt is the reflexive possessive form. It is used when the possessor is the same as the subject of the sentence.

Here, the subject is hann (he), and the beard belongs to that same person. So Icelandic uses sinn/sín/sitt.

• skeggið sitt = his own beard

If you used hans, it would usually mean his in the sense of some other male person's, not the subject himself.

So the contrast is roughly:

• Hann ... skeggið sitt = He ... his own beard
• Hann ... skeggið hans = He ... his beard (someone else’s beard)

Because sinn changes to agree with the noun it describes.

The noun here is skeggið:

• skegg is neuter
• it is singular
• in this sentence it is the direct object

So the reflexive possessive appears as sitt, the neuter singular form.

Compare:

• sinn for some masculine singular nouns
• sína for some feminine forms / plural / different cases
• sitt for neuter singular here

So sitt matches skeggið.

It is the direct object of snyrta, so it is in the accusative.

However, for many neuter nouns in Icelandic, the nominative and accusative forms are identical in the singular. So even though it is accusative here, it still appears as skeggið.

That is why you do not see a visible change in the form.

Yes, á morgun is a very common and natural way to say tomorrow.

Literally, it is built from:

• á = on
• morgun = morning / tomorrow in this expression

But as a whole expression, á morgun simply means tomorrow.

So:

• í dag = today
• á morgun = tomorrow
• í gær = yesterday

You should learn á morgun as a fixed everyday expression.

That is a very normal Icelandic word order. Time expressions often come later in the sentence.

So the structure is:

• Hann = subject
• ætlar að = is going to / plans to
• láta snyrta = have trimmed
• skeggið sitt = his beard
• á morgun = tomorrow

You could move á morgun earlier for emphasis, but the version given is completely natural and neutral.

No, the most natural reading is that someone else will do it for him.

Because of láta + infinitive, the sentence means he will have his beard trimmed or get his beard trimmed.

If you wanted to say that he himself will trim his beard, Icelandic would normally use a different structure, for example with a verb meaning trim where he is directly doing the action himself.

Yes. Common natural translations include:

• He is going to have his beard trimmed tomorrow.
• He plans to get his beard trimmed tomorrow.
• He is going to have his beard groomed tomorrow.

The best choice depends on context, but all of them reflect the Icelandic sentence well.