I've just checked the dictionary about the meaning of the idiom "concerned with" and I found it as a synonym of "interested in". Then I can use "concerned with" in any place of "interested in", or there are some exceptions that I should know?
For example, if I want to buy a nice car, can I say "I'm concerned with this car"? or "I'm concerned with this girl" and so on?
In the same topic, I'd like to know if I can use "concern with" in the past form without "to be" before. (e.i. instead of using "he was concerned with this car", I would omit the "to be" auxiliary verb and I'd say "He concerned with this car")