When I have to describe some situations or people charachers, I become really annoyed as no other adjectives except for 'good' and 'bad' come to my mind. Could you give me some advice about how I can fill in the gaps in this part of vocabulary?
I strongly second RonBee's suggestion that you consult a thesaurus.
Also, it will be good for you to keep reading, reading, reading, since it is often the case that synonyms have important shadings of meaning. It's a tricky business, even for native speakers (of any language, I presume).
All best wishes,
You could try these:
What are some adjectives that describe a person's personality? - Yahoo! Answers
ADJECTIVES. English vocabulary builder with instant answers. Tests, games to improve vocabulary
A Google search for "adjective person" and "adjective situation" will give you more.