Wanjai, You have the correct meaning for "I scared you" - another way of saying it would be - "I made you feel fear" or "I frightened you" . "I am scared" means that the person speaking is afraid which is the opposite to "I am scary" which means the person talking is causing other people to be afraid. Does that help?

You are scare, You look terrible, like monster, or you're doing bad things like killer. You are scared, You're afraid alot, You feel strong fear .

Not that relevant, but this reminded me of the song 'I scare myself' from Thomas Dolby. May-be you can listen to the lyrics to make the word clearer.