Ég hef mikinn tíma í dag.

Hef is the 1st person singular present tense of the verb að hafa (to have).

So:

• ég hef = I have
• þú hefur = you have
• hann/hún/það hefur = he/she/it has

In this sentence, ég hef is simply the normal way to say I have.

Because tími is the direct object of hef, and after að hafa the direct object is usually in the accusative case.

The basic dictionary form is:

• mikill tími = much time / a lot of time in the nominative

But in this sentence, the object has to be accusative:

• mikinn tíma

Both the adjective and the noun change form:

• mikill → mikinn
• tími → tíma

So this is an example of adjective + noun agreement in gender, number, and case.

Tíma is accusative singular.

Why? Because it is the object of the verb að hafa. In Icelandic, many verbs require their direct object to be in the accusative, and að hafa is one of them.

So:

• ég hef tíma = I have time
• tími is the dictionary form, but
• tíma is the form used here because of the accusative

In Icelandic, adjectives must agree with the noun they describe.

That means the adjective changes according to the noun’s:

• gender
• number
• case

Here, tími is:

• masculine
• singular
• accusative

So the adjective must match that:

• nominative masculine singular: mikill
• accusative masculine singular: mikinn

That is why you get mikinn tíma.

It can be understood as much time, but in natural English it is usually translated as a lot of time.

So although the Icelandic wording is close to much time, the normal sense is:

• I have a lot of time today

This is a very common Icelandic way to express that idea.

Icelandic does not have an indefinite article like English a/an.

So where English says:

• a time
• a book
• a day

Icelandic often just uses the noun by itself:

• tími
• bók
• dagur

In this sentence, mikinn tíma already means something like a lot of time, so no separate word for a is needed.

Í dag means today.

Literally, í often means in, and dag is related to day, but í dag functions as a fixed everyday expression meaning today.

So:

• í dag = today

This is very common in Icelandic and is best learned as a set phrase.

Putting í dag at the end is a very normal word order in Icelandic.

The sentence structure is:

• Ég = subject
• hef = verb
• mikinn tíma = object
• í dag = time expression

So the order is basically:

Subject + Verb + Object + Time

That is completely natural.

You can sometimes move time expressions for emphasis, for example:

• Í dag hef ég mikinn tíma.

That still means the same thing, but it gives today more emphasis.

Usually, no. Icelandic normally keeps the subject pronoun.

So you would say:

• Ég hef mikinn tíma í dag.

Unlike some languages, Icelandic does not usually drop the subject pronoun in ordinary sentences.

A rough English-friendly guide would be:

• Ég ≈ yeg / yeh-g
• hef ≈ hev
• mikinn ≈ MIH-kinn
• tíma ≈ TEE-ma
• í dag ≈ ee daoug / ee daag depending on accent

A few useful notes:

• é sounds like ye in many contexts
• í sounds like ee
• á is like ow in now, though pronunciation can vary by context and speaker
• Icelandic pronunciation is not always obvious from spelling, so listening to native audio is very helpful

Yes.

• Ég hef tíma í dag = I have time today
• Ég hef mikinn tíma í dag = I have a lot of time today

So adding mikinn makes the amount stronger. Without it, the sentence is more neutral and simply says that you do have time available.

The dictionary forms are:

• ég = I
• að hafa = to have
• mikill = big / much / great, depending on context
• tími = time
• í dag = today (fixed expression)

In the sentence, some words appear in changed forms because of grammar:

• hef comes from að hafa
• mikinn comes from mikill
• tíma comes from tími