I would like a literature review for developing my business

I intend to offe rpersonalised 1 to 1 communication and language support to a) doctors b) other healthcare professionals whose first language is not English. I would like someone to find out if there is any evidence that 1 to 1 tuition is better for learners than something like duolingo or learning from youtube videos. And then to write a 1-2 page summary I could use parts of in my marketing. If there is no evidence then there is no need to write anything. Budget assumes there is. I don't know how much literature there is so would be prepared to discuss budget.