mastered
v.v. to learn a skill or a language so well that you have no more difficulties with it. You use this when you have reached a very high level of ability.
v. to acquire complete knowledge or command of a subject or skill through intensive study or practice. Often implies the transition from a learner to an expert or proficient user.
She mastered the guitar after years of daily practice.
By the end of the intensive course, most students had mastered the basics of coding.
While many scholars have studied the ancient dialect, few have truly mastered its complex tonal shifts and idiomatic nuances to the point of native-like fluency.
The verb is transitive and requires a direct object, typically a skill, language, or subject.
He is mastered in FrenchHe has mastered FrenchMastered is the past participle of a transitive verb, not an adjective describing a person's state; use 'has mastered' or 'is proficient in'.