Feeling confused with mixed methods and survey analysis

Hi
I need some advice regarding what type of analysis I should do, maybe mixed method, using thematic analysis with quantitative analysis. I am a bit lost as it is quite confusing. In my study I have to investigate the marketing strategies adopted by the international fast food entrants in India and what difficulties they face. Also, I want to evaluate that why people prefer them over the local restaurants. For that, I am thinking to interview the employees of the restaurants and the customers who visit there. In this way, I will understand the opinions of both the sides. I am a bit lost here, should I interview the employees and conduct survey (like distributing questionnaire) with the customers? How much sample size should I take? In which method (interview or survey) can I do thematic analysis and quantitative analysis?

Posted in: Survey and Analysis