Kerstin, Welcome to the forum - suggestions would depend on what genre you're looking at for the feature and how long.
comedy, romance, drama, adventure, sci-fi, all of the above?
local to the phillipines, something closer to your native culture?
also - you say screen writing, not filming, so can you take a short story or novella and rewrite it for a screenplay, or does this have to be a completely original work?
if adaption, it would be fairly simple to modernize a great many classic works of literature, such as The Metamorphosis by Franz Kafka, anything by Jorge Borges, or possibly William Porter.
If documentary type things, perhaps something showing a correlation between loss of native habitat and extinction events among indigenous cultures around the world -- Bushmen, Pygmies, Inu, Sami, etc...
then there's always the classic bumbling criminal type shoot em ups ala CLint Eastwood's "Any Which Way" movies, "lock, stock and 2 smoking barrels" or "the way of the gun".
hope this helps.
and keep us posted!