Excellent post Benelima!
The answer to your question is not a different verb tense but the "Passive Voice
Passive voice is used when the subject in the sentence (sujeito) is unknown or in the sentences where the subject is there but it is not important, or not the most important piece of information (maybe you do not want to highlight the subject).
We see passive voice more in written English, is formal, but very useful.
Many things have been done... Improvements have been done...
We have two past participle verbs
" and "done
", the first is part of the perfect tense and the second is used because of passive voice.