Is Language Learned Or Acquired?

This is a psychology research topic is whether language is learned or acquired. Do those who have

learned a language have the ability to perform the same if not better grammatically and verbally versus

native speakers?
Perhaps early on to a child's life they spoke a particular language, however became less fluent as they

grew up and wanted to reintroduce themselves into the grammar and vocabulary, would a person who is

completely new to the same language have the ability to understand and speak said language better than

the person who initially grew up with knowledge of the language?