Sápan er ekki hér, því miður.

sápa is the indefinite form (a soap / soap).
sápan is the definite form (the soap), where Icelandic typically attaches the definite article to the end of the noun:

• sápa = a soap / soap
• sápan = the soap
  The -n is the “the”-ending for many feminine nouns in the singular nominative.

sápa is feminine. Gender matters because it affects:

• the definite ending (sápan)
• case endings in other roles (object forms, after prepositions, etc.)
  In this sentence, it’s the subject (nominative), so you see the nominative definite form sápan.

er is the present tense, 3rd person singular form of the verb vera (to be):

• ég er = I am
• þú ert = you are
• hann/hún/það er = he/she/it is
  So Sápan er ... = The soap is ...

In a neutral statement, Icelandic typically follows a pattern like: Subject – verb – negation/adverbs – rest
So Sápan er ekki hér is the natural default.

You can move things for emphasis or style, but ekki normally comes after the finite verb (er) in a basic main clause.

In most main-clause statements, ekki usually comes after the conjugated verb:

• Ég sé ekki = I don’t see
• Hún kemur ekki = She isn’t coming
• Sápan er ekki hér = The soap isn’t here

If there’s an auxiliary + infinitive, ekki often goes after the auxiliary:

• Ég get ekki farið = I can’t go

hér means here.
hérna is also common and often feels a bit more conversational/emphatic (roughly “right here”), depending on speaker/style.

So these can both work:

• Sápan er ekki hér.
• Sápan er ekki hérna.

It’s common to use a comma when því miður is added as a parenthetical comment:

• Sápan er ekki hér, því miður. = The soap isn’t here, unfortunately.

You may also see it without a comma, especially in shorter/less formal writing:

• Sápan er ekki hér því miður.

Yes. It’s very natural:

• Því miður er sápan ekki hér.

Notice two things: 1) The verb still comes early (typical Icelandic “verb-second” behavior in main clauses).
2) sápan is not capitalized mid-sentence: ... er sápan ...

It’s capitalized only because it’s the first word of the sentence. Icelandic does not capitalize common nouns otherwise:

• Sápan er ekki hér. (start of sentence)
• Því miður er sápan ekki hér. (mid-sentence)

Key points:

• á is a different vowel from a (a clear “ow/au”-like vowel in Icelandic).
• þ is like English th in thing (voiceless).
• é is like “yeh/eh” with a y-glide in many accents.

A rough approximation:

• Sápan ≈ “SOW-pan” (with Icelandic vowel quality)
• er ≈ “ehr”
• ekki ≈ “EHK-ki”
• hér ≈ “hyehr”
• því ≈ “thvee”
• miður ≈ “MIH-thur” / “MIH-ur” (varies by speaker; ð is often a soft “th” like in this, or can be very light)

Common singular forms (useful for basic sentences):

• Nominative: sápa / sápan (subject: “a soap / the soap”)
• Accusative: sápu / sápuna (direct object)
• Dative: sápu / sápunni (after many prepositions, “to/for/at the soap”)
• Genitive: sápu / sápunnar (“of the soap”)