Estic bé avui.

Estic is the first-person singular present tense form of estar. In other words, it means I am.

So:

• estic = I am
• estar = to be

Catalan has two main verbs that can mean to be: ser and estar.

In this sentence, estar is used because it describes a state or condition: how someone feels, physically or emotionally, at that moment.

So:

• Estic bé = I’m fine / I’m well
• Sóc is used more for identity, origin, profession, and other more inherent facts, like Sóc anglès or Sóc professor.

Catalan often leaves out subject pronouns because the verb ending already tells you who the subject is.

Here, estic already clearly means I am, so jo is not necessary.

You could say Jo estic bé avui, but that usually adds emphasis, contrast, or clarity:

• Jo estic bé avui, però ell no.

Bé is the word used for well / fine in this kind of sentence.

A useful contrast is:

• bé = well, fine
• bo / bona = good as an adjective

So:

• Estic bé = I’m fine / well
• És una bona idea = It’s a good idea

English often uses good where Catalan uses bé, so this is a very common thing for learners to notice.

The accent mark is important. It shows that the word is stressed and helps indicate the vowel sound.

So bé is written with an accent, and you should learn it as a complete word: bé.

In practice, it is pronounced roughly like bay, though exact pronunciation varies a bit by dialect.

Yes. Catalan word order is fairly flexible, especially with time words like avui.

All of these are possible:

• Estic bé avui.
• Avui estic bé.

Both are natural. Putting avui first can give it a bit more emphasis, like As for today, I’m fine.

Also, avui does not need a preposition. It is already an adverb meaning today.

A rough English-friendly guide would be:

uh-STEEK bay uh-BOOY

That is only an approximation, and pronunciation changes somewhat by dialect, but it is close enough for a beginner.

A few helpful notes:

• estic has the stress on the second syllable
• bé is short and stressed
• avui is stressed on the second syllable

Yes, it is perfectly natural. It sounds like a normal way to say that you are fine today.

Depending on context, a speaker might also say:

• Avui estic bé.
• Estic molt bé avui. for I’m very well today

But Estic bé avui is absolutely normal Catalan.