My recommendation to you is forget all the numbo jumbo grammatical terms and concentrate on the basics -- meanings, subject-verb agreement. The best way to master the English language is not to analyze the grammatical structure to death. Grammar is useful for foreign students to understand the syntax and meaning and to avoid committing the common grammatical errors that show you are uneducated. No need to question why this syntax but not that syntax. Grammar describes what is out there, not why it is out there.
Hope you get the idea.