Hann minnir mig á fundinn í hádeginu.

minna means to remind. The common pattern is:
minna + (person in accusative) + á + (thing in accusative)
So Hann minnir mig á fundinn = He reminds me of/about the meeting (i.e., he causes me to remember it).

Because mig is the accusative form of ég (I/me).
In minna (einhvern) á (eitthvað), the person being reminded is the direct object, and direct objects are often in the accusative in Icelandic.

• ég = I (subject)
• mig = me (object)

With minna, Icelandic normally uses the preposition á (roughly of/about).
That á then takes the accusative in this construction, so fundur (meeting) becomes fundinn (accusative singular definite).

Yes. fundinn is:

• noun: fundur (meeting)
• case/number: accusative singular
• definiteness: definite (the -inn ending = “the”)

So fundinn = the meeting (specifically, as an accusative object after á here).

í often means in/at, and with time-when expressions it commonly takes the dative.
hádegi is a neuter noun meaning noon / midday, and the form hádeginu is dative singular definite (“at noon / at midday”).

Often yes. um hádegi is very common for around/at noon.

• um hádegi: focuses on the time point/around that time
• í hádeginu: can feel like at midday / during midday, using a “within that time” framing
  Both can be translated as at noon in many contexts.

It’s flexible, but Icelandic is verb-second (V2) in main clauses: the finite verb tends to come second.
You can move time phrases forward for emphasis:

• Í hádeginu minnir hann mig á fundinn. (At noon, he reminds me of the meeting.)
  Or move the object phrase:
• Hann minnir mig á fundinn í hádeginu. (neutral)

Yes, with the same structure minna mig á X, it can mean either: 1) remind me of X (make me think of / remember)
2) resemble X (make me think of because of similarity)

In this sentence, because fundinn is an event (a meeting), the natural reading is the “remind me about/of (the meeting)” meaning, not physical resemblance.

minnir is present tense, 3rd person singular: he reminds.
The past is typically minnti:

• Hann minnti mig á fundinn í hádeginu. = He reminded me of the meeting at noon.

A practical approximation:

• Hann ≈ hatn (the nn is often a “pre-stopped” sound)
• minnir ≈ MIN-nir (stress on the first syllable)
• mig ≈ mig (short i)
• á = ow/au (a diphthong, not a long plain “ah”)
• fundinn ≈ FUN-din (with the same kind of nn effect at the end)
• í hádeginu ≈ ee HOW-they-nee-noo (roughly; stress on há-)