Yes, research shows that effective language teachers improve student language learning. They use good teaching methods, give helpful feedback, and create engaging classes. Teacher skills and ongoing training are important for student success.

John Hattie's well-known study ("Visible Learning") examines many variables that either refer to or are controlled by the teacher (e.g., teacher clarity, teacher feedback). The study shows their effectiveness on the students' learning outcomes. Since the study's results apply to the classroom as such (independent of the subject), they would also apply - to the best of our knowledge - to the foreign-language classroom (unless shown otherwise).

See David Nunan "Second Language Teaching and Learning" 1999. There is an extract in Google Books.

See also the postulate on "implicit learning" and "explicit learning" by R. Ellis (example: https://websites.umich.edu/~ncellis/NickEllis/Publications_files/Implicit_AND_Explicit_Learning_EllisPreprint.pdf)

Good luck!

Yes, I have conducted a research on the importance of English Literature in English Teaching in which the English Language is taught through Literature. English Language can be more effective if it is taught in English Literature. The research explore how the English Language can be more effective if it is taught through.

You may also want to look at the literature on Evidence-Based Practice and teacher (self)-efficacy.