Translation:The people do not stop expressing how they feel.
Here "para" is not a preposition, it is the 3rd pers. sing of parar = to stop; "O povo não para" = "the people do not stop". Parar de + infinitive = Stop +present participle. Therefore "O povo não para de demonstrar ..." = "The people do not stop expressing ..."
povo is singular, unlike the English people (which also used to be singular). See the discussion above.
Is the progressive required here? To my non native English ears "the people don't stop to show/express how they feel" sounds at least acceptable to.
In standard English it would be "The people haven't stopped expressing how they feel". (Action started in the past and continues to this moment in time - ongoing action that affects the present).
Shouldn't "the people" when it is the translation of "o povo" be singular? Like "the nation"?
Interesting. Apparently this has changed not too long ago:
The ox knows its owner, and the ass its master's crib; but Israel does not know, my people does not understand.
(Old Testament, Revised Standard Version, 1952 —Isaiah 1:3)
Here 'people' is like 'povo' in Portuguese, not like 'pessoas'.
I don't think that the OT is a really good source for standard English. However, this is what I have found:
"The ox knows its owner and the donkey its master's feeding rack; but Israel does not understand; My people show themselves lacking in discernment". The Revised Berkeley version in Modern English - 1986 edition.
OK, so it seems something changed between 1952 and 1986. I looked up a lot of translations and all the modern ones have the verb in plural. Whereas the Revised Standard version has the verb in singular, the New Revised Standard Version (1989, 1995) has plural. Of course the real old ones have 'doth' or 'hath', which I think is also singular.
This is not my experience of various major English dialects. It is singular when referring to a category of individuals seen as a cultural or political unit.
For example, they are a people; when a people.
Should this translation not also be accepted: "the people do not stop to demonstrate how they feel"