Ef ég hefði meiri tíma, myndi ég baka litla pítsu með sveppum og hvítlauk í kvöld.

It is a hypothetical / unreal conditional about the present or future.

• Ef ég hefði meiri tíma = If I had more time
• myndi ég baka ... í kvöld = I would bake ... tonight

So the speaker is not talking about a real situation they expect to happen; they are imagining it.

Hefði is the past subjunctive form of hafa (to have).

In Icelandic, unreal or hypothetical if clauses often use:

• ef + past subjunctive
• then myndi + infinitive in the main clause

So:

• hefur = has / have (present, factual)
• hafði = had (past, factual)
• hefði = had in a hypothetical sense

That is why ef ég hefði meiri tíma means if I had more time in the unreal, imagined sense.

This works a lot like English.

English says:

• If I had more time, I would bake...

Even though had looks past, the meaning is not really past time. It means the situation is not true now or is contrary to reality.

Icelandic does the same thing:

• hefði and myndi look past historically,
• but together they signal a present/future hypothetical.

If the sentence were really about an unreal past, Icelandic would use a different structure, for example something like Ef ég hefði haft meiri tíma...

Because the two clauses follow different word-order rules.

In the ef clause

Ef introduces a subordinate clause, so normal subordinate-clause order is used:

• ef ég hefði
• not ef hefði ég

In the main clause

Icelandic main clauses follow the V2 rule: the finite verb normally comes in the second position.

Since the whole ef clause comes first, the next clause begins with the finite verb:

• myndi ég baka

If the sentence started directly with the main clause, you would get:

• Ég myndi baka litla pítsu...

So the word order changes because the sentence begins with a fronted subordinate clause.

Because Icelandic has no indefinite article.

So a bare noun can mean:

• a small pizza
• one small pizza

depending on context.

That is why litla pítsu can naturally mean a small pizza without a separate word for a.

By contrast, Icelandic usually expresses the with a suffix on the noun:

• pítsa = pizza / a pizza
• pítsan = the pizza

Meiri means more. It is the comparative form of mikill.

So:

• mikill tími = a lot of time / much time
• meiri tími = more time

In this sentence, tíma is the direct object of hafa, so it appears in the accusative:

• nominative: tími
• accusative: tíma

So meiri tíma means more time, with tíma in the form required by the verb.

Because the noun phrase is in the accusative singular, since it is the direct object of baka.

• nominative: lítil pítsa = a small pizza
• accusative: litla pítsu = a small pizza (as an object)

Both the adjective and the noun change form:

• pítsa → pítsu
• lítil → litla

This is normal Icelandic agreement: the adjective must match the noun in gender, number, and case.

Here með means with, and in this usage it takes the dative.

So the nouns after it appear in dative forms:

• sveppur → sveppum (dative plural)
• hvítlaukur → hvítlauk (dative singular)

So:

• með sveppum = with mushrooms
• með hvítlauk = with garlic

It is also natural that sveppum is plural but hvítlauk is singular, because garlic is often treated like an ingredient or mass noun rather than a countable item.

Í kvöld is a standard Icelandic time expression meaning tonight / this evening.

It is best learned as a fixed phrase, just like:

• í dag = today
• í nótt = tonight / during the night
• í morgun = this morning

So even though í often literally means in, the whole phrase í kvöld should be understood as the normal idiomatic way to say tonight.

Because the sentence begins with a subordinate clause:

• Ef ég hefði meiri tíma, ...

In Icelandic writing, it is normal to separate that subordinate clause from the main clause with a comma.

So the comma helps show the structure:

• subordinate clause: Ef ég hefði meiri tíma
• main clause: myndi ég baka litla pítsu með sveppum og hvítlauk í kvöld

It is doing the same job as in English sentences like If I had more time, I would bake...