Why does the writer think that it’s not difficult to write about what constitutes correct English?
He thinks it’s relatively easy to do with the help of the Oxford English Dictionary and some reputable grammar books by way of research.
How did the writer get a clear understanding of how English had imported words from other languages?
By having studied French, Latin and Greek
What did studying English at the university force him to focus intently on?
Studying English at the university forced him to focus on what words actually meant.