Below you'll find links to interesting content and research related to natural language acquisition
Dr. Stephen Krashen’s website (the father of natural language acquisition research)
https://www.sdkrashen.com/
An overview of Dr. Krashen’s main hypotheses
https://www.sk.com.br/sk-krash-english.html
BBC article on the benefits of being bilingual
https://www.bbc.com/future/article/20160811-the-amazing-benefits-of-being-bilingual