Progressive: Estar a + Infinitive
In European Portuguese, ongoing actions are expressed with estar a + infinitive. This is one of the most important structural differences from Brazilian Portuguese, which uses the gerund.
PortuStories Editorial
European Portuguese Grammar Guide
To say something is happening right now in European Portuguese, combine estar with the preposition a followed by the infinitive of the main verb. This construction is the progressive or continuous aspect.
Estou a comer.
I am eating.
Literally: I am at eating.
Ela está a trabalhar.
She is working.
Eles estão a falar muito alto.
They are speaking very loudly.
🇵🇹 European Portuguese
Estou a ler um livro.
🇧🇷 Brazilian Portuguese
Estou lendo um livro.
EP uses estar a + infinitive; BP drops the preposition and uses the gerund (-ndo).
The preposition a is never dropped in EP. Saying "estou comendo" immediately marks you as a Brazilian Portuguese speaker and sounds foreign in Portugal.
The pattern extends to all tenses of estar: estava a (past progressive), vou estar a (future).
Estava a chover quando saí.
It was raining when I left.
From a PortuStories Story
O João está a fazer o jantar enquanto a Maria está a pôr a mesa.
João is making dinner while Maria is setting the table.