Hey Adnan,
I’d imagine FUDs on online surveys are pretty common! 
I’m hoping an expert like @alex_birkett or @emma can chime in here.
If you’re worried about distracting people from the purchase, perhaps start with putting the survey after the purchase, on the thank-you page?
When it comes to questions; see if this is useful: Write good survey questions. It has some concrete examples of questions to ask at specific stages.
Pre-empting bounces: My thought would be to dig into your analytics and see how long people generally wait on a page before bouncing, and set your survey timing a little lower than the median.