Any advise who is flying, how frequently and how to contact the operator/carrier? I have not find any information on the internet. Any info is appreciated
The best starting point for the less busy airports is to consult their official pages such as Port of Spain, which lists the flight VO 4005 departed at 5:30PM by Conviasa Airlines, which seems to be the only airline flying the direct route.
Parlomar's Wiki page lists 2 other airlines that make such a flight but I think they are private charters for the most part.
My usual go-to resource for flight schedules out of a particular airport is kayak: All you need is the IATA airport code for your origin (in this case POS) and you can just go straight to:
to see that there are three flights a week, operated by Conviasa. You can then check on the airline's website for more information.