So if I wanted to say to be improved, should I use verbessert werden or sich verbessern?
z.B.
Es kann verbessert werden.
Oder...
Es kann sich verbessern.
"Es kann sich verbessern"
implies that "it" can improve itself.
"It" can be the weather, for instance.
"Es kann verbessert werden"
means that someone else can improve "it".
"It" can be the weather control machine, for instance :)
to be improved is passive (vs. "to improve") and probably should be translated with passive.
Es kann verbessert werden
There is a single German word addressing all genders and things:
Verbesserungswürdig