Thanks for your message. You cannot deduce the number of persons to be
surveyed by calculating the proportion from the total population. While
the sample in the study conducted by the City ofistanbul is
representative, yours is not. You need more cases for your survey to be
representative. However, you could argue that your survey need not be
representative. It is an exploratory study. Best ask someone who is
familiar with quantitative methods, above all sampling.

Your questionnaire looks good to me.

No, you do not need to ask EC for approval.

Let me know if you have further questions.

Best wishes,