Bon ou bien

Bon/ mauvais are usually an adjectives. They modifie a noun and means good/ bad, suitable/ unsuitable, correct/ wrong, etc.

Bien mal are usually used as adverbs. They mean well /badly or can be used to stress something.
Bien / mal can only be used as adjectives with state-of-being verbs such as être.

Bon, in the rare instances where it is used as an adverb, means good or pleasant.

Bon, in the rare instances where it is used as an adverb, means good or pleasant in these expressions.
Cà sent bon = It smells good
Ça goûte bon = It tastes good
Ça sonne bon = It sounds good