If/whenever people eat too much, they feel uncomfortable. [general truth - type 0 conditional]
If I spoke English fluently, I would quit my job and find a better one. [hypothetical present/future situation - type 2 conditional]
If I don't pay my bills, I will get punished by the law. [real present/future situation - type 1 conditional]
If you sit in the sun for too long, your skin
will feel painful. [this is a type 1 conditional if it is said at the beach to a person]