I finished …ing
Não terminei de ler este livro.
I haven't finished reading this book.
Terminei de escrever uma carta.
I finished writing a letter.
I finished lunch.
Eu ainda não terminei de ler este livro.
I still haven't finished reading this book.
Terminei de ler o livro que estava lendo.
I finished reading the book I was reading.
I finished studying.
I've already finished studying.
I haven't finished doing that.