Your writing is grammatically correct, congraulations.

But I would like to give you an example of how I, as a native Chinese speaker, would write a self-introduction on internet.

你 好！ 我 叫 弗拉維亞。 我 来自 巴西。 我 二十八 岁。 我 讲 葡萄牙語。

你好，我叫芙拉维娅，我是巴西人，今年二十八岁，母语是葡萄牙语。

reasons:

1. 芙拉维娅 is more feminine than "弗拉维亚"。

2. If you are in another country, it's absolutely right to say that "我 来自 巴西"， but on internet, I suggest you say "我是巴西人", well, not strongly advise.

3. ”我讲葡萄牙语“， and "我会讲葡萄牙语", from personal perspective, I think it's inapproprite, these two sentences are referring that either I speak Portuguese and some other languages, or Portuguese is not my mother tongue, but a foreign language that I'm capable of speaking it fluently.

Virtual scene : My mother is Italian, father is Chinese, I was born in China, and raised in Spain, and then went to American for college where I studied Esperanto, then I can say:" Hi, bitches, 我讲中文，英语，西班牙语，意大利语, 我还在学世界语。"

So, I think in the context, "我的母语是葡萄牙语" is the right expression.

My first Chinese Note =)

你 好！ 我 叫 弗拉維亞。 我 来自 巴西。 我 二十八 岁。 我 讲 葡萄牙語。

In simplified Chinese

你好!我叫弗拉維维亞。我来自巴西。我二十八岁。我讲葡萄牙语。

In traditional Chinese

你好！我叫弗拉維亞。我來自巴西。我二十八歲。我講葡萄牙語。

My first Chinese Note =)

你 好！ 我 叫 弗拉維亞， 我来自巴西， 二十八 岁，讲葡萄牙語的。

My first Chinese Note =)

你 好！ 我 叫 弗拉維亞。 我 来自 巴西。 我 二十八 岁。 我 讲 葡萄牙語。

你好！ 我叫弗拉維亞， 28岁， 来自巴西，讲葡萄牙语。。。。