No, you would say - good behaviour and the adjective is well-behaved.
The noun behavior has the adjective form behavioral. (The UK spelling is behavioural.)
unusualsuspiciouswrecklesstimidenthusiasticreticentcourageousaudaciousheroiccautiousmodest
behavioral
The word well is an adjective, for example well water or well wisher.
Fearless is an adjective because it is a descriptive word.
As a verb, "explaining behavior" is the act of using words to explain a behavior. As an adjective, "explaining behavior" is the observable behavior in which a person tends to explain her/himself.
Stubborn is an adjective, because it describes something.
Well, an adjective for bee is 'bumble.'
The word "ungentlemanly" is an adjective. It describes a behavior or action that is not characteristic of a gentleman.
The word "frantic" is an adjective. It describes a state of wild or frenzied activity or behavior.
It is well with you
annoying, obvious, nosy