Eu tenho medo de falar na reunião online.

Yes. In Brazilian Portuguese, subject pronouns are often omitted when the verb already makes the subject clear.

So:

• Eu tenho medo de falar na reunião online.
• Tenho medo de falar na reunião online.

Both are natural.

People often include eu for emphasis, contrast, or clarity, such as:

• Eu tenho medo, mas ela não.
  = I’m afraid, but she isn’t.

Because tenho clearly means I have, the eu is not required.

Ter medo de is a very common Portuguese structure meaning to be afraid of or to be afraid to do something.

It works like this:

• ter = to have
• medo = fear
• de = of / to

So:

• tenho medo de falar = I’m afraid to speak
• tenho medo de errar = I’m afraid of making mistakes
• tenho medo de cachorro = I’m afraid of dogs

This is one of those patterns you should learn as a chunk:

ter medo de + noun / infinitive

After tenho medo de, Portuguese normally uses the infinitive when talking about an action in general.

So:

• tenho medo de falar = I’m afraid to speak / of speaking

Using falando here would not sound right in standard Portuguese.

A useful pattern is:

• medo de + infinitive

Examples:

• Tenho medo de viajar sozinho.
• Ela tem medo de dirigir.
• Temos medo de esquecer tudo.

So falar is used because it is the base verb form after de in this structure.

Na is a contraction of:

• em
  • a = na

So:

• na reunião = in the meeting / at the meeting

This kind of contraction is very common in Portuguese:

• em + o = no
• em + a = na
• em + os = nos
• em + as = nas

Examples:

• no carro = in the car
• na escola = at school
• nos livros = in the books
• nas reuniões = in the meetings

Because reunião here is being used with the definite article a:

• em + a reunião → na reunião

This usually suggests a more specific meeting, often one that the speaker and listener can identify from context.

Compare:

• falar na reunião online = speak in/at the online meeting
• falar em uma reunião online = speak in an online meeting

So na reunião online often feels like a particular meeting, not just meetings in general.

It means speak in/at the meeting.

This is an important distinction, because Portuguese changes the preposition depending on the meaning:

• falar na reunião = speak at/in the meeting
• falar da reunião = talk about the meeting
• falar com alguém = speak with someone
• falar sobre algo = talk about something

So in your sentence, na reunião tells us where the speaking happens.

In Portuguese, adjectives usually come after the noun.

So:

• reunião online
• curso online
• aula online

That is the most natural order.

Since online is a borrowed word used like an adjective, it usually stays after the noun just like many other adjectives in Portuguese.

You may also hear alternatives like:

• reunião virtual
• reunião pela internet

But reunião online is very common and natural in Brazilian Portuguese.

Usually, Brazilians pronounce it in a Portuguese-influenced way, often something like on-LAI-ni or a similar local adaptation.

The exact pronunciation can vary, but the important point for learners is:

• it is a borrowed word
• it does not change form
• it is widely understood

You do not need a perfect English-style pronunciation for Brazilians to understand you.

Reunião can be tricky because of the nasal ending -ão.

A rough guide is:

• reu sounds something like reh-oo
• ni sounds like nee
• ão is a nasal sound, roughly like ow̃

A rough approximation for English speakers is:

reh-oo-nee-OW̃

The stress is on the last syllable:

• re-u-ni-ÃO

The ending -ão is very common in Portuguese:

• reunião
• situação
• informação
• opinião

That nasal sound does not exist in English in the same way, so it takes practice.

Yes. That is also very natural.

Compare:

• Tenho medo de falar na reunião online.
• Estou com medo de falar na reunião online.

Both can mean I’m afraid to speak in the online meeting, but there is a slight nuance:

• tenho medo de can sound more like a general fear or personal tendency
• estou com medo de can sound more like how you feel right now, at this moment

In everyday Brazilian Portuguese, both are common.

Yes. Falar is a very broad verb and can cover both speak and talk depending on context.

For example:

• falar português = speak Portuguese
• falar com ela = talk to her
• falar na reunião = speak at the meeting

So in your sentence, falar is best understood as speak or talk during the meeting.

Yes, a little.

Compare:

• na reunião online = in/at the online meeting
• em uma reunião online = in/at an online meeting

So:

• Tenho medo de falar na reunião online.
  suggests a specific meeting

• Tenho medo de falar em uma reunião online.
  suggests online meetings more generally, or any one online meeting

Both are correct. The choice depends on whether the meeting is specific or not.

Yes, it is completely natural.

It sounds like something a Brazilian Portuguese speaker might really say, especially in work, school, or professional contexts.

Very natural alternatives include:

• Tenho medo de falar na reunião.
• Tenho medo de falar na reunião online da empresa.
• Estou com medo de falar na reunião online.

Your original sentence is clear, grammatical, and idiomatic.