Acabar de + Infinitive: Just Finished
The construction acabar de + infinitive expresses that something has just happened. It is used in the present or imperfect tense and is equivalent to English "to have just done something".
PortuStories Editorial
European Portuguese Grammar Guide
Acabar de + infinitive in the present tense means "to have just done" something very recently.
Acabei de chegar.
I have just arrived.
Ela acabou de telefonar.
She has just called.
In the imperfect, acabar de expresses the "just past" relative to a past narrative moment.
Quando entraste, eu acabava de adormecer.
When you came in, I had just fallen asleep.
This construction is always followed by the plain (impersonal) infinitive, never the personal infinitive. Acabei de comer — not acabei de comeres.
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Não podes falar com ela agora — acabou de sair.
You can't speak to her now — she has just left.